docs: fix changelog header to consistent size (#228)

Co-authored-by: Anthonios Partheniou <partheniou@google.com>

Author: dandhlee

CHANGELOG.md

@@ -1,6 +1,6 @@
 # Changelog
 
-### [0.8.1](https://github.com/googleapis/python-analytics-admin/compare/v0.8.0...v0.8.1) (2022-05-13)
+## [0.8.1](https://github.com/googleapis/python-analytics-admin/compare/v0.8.0...v0.8.1) (2022-05-13)
 
 
 ### Bug Fixes
@@ -36,7 +36,7 @@
 * add autogenerated code snippets ([323815a](https://github.com/googleapis/python-analytics-admin/commit/323815a140de25fe75e7e9c9f45fdaa45c71ce35))
 * update the documentation with a new list of valid values for `UserLink.direct_roles` field ([03abb54](https://github.com/googleapis/python-analytics-admin/commit/03abb54e9a394bb4f69203c98099a5e628116b48))
 
-### [0.7.2](https://www.github.com/googleapis/python-analytics-admin/compare/v0.7.1...v0.7.2) (2021-11-01)
+## [0.7.2](https://www.github.com/googleapis/python-analytics-admin/compare/v0.7.1...v0.7.2) (2021-11-01)
 
 
 ### Bug Fixes
@@ -49,7 +49,7 @@
 
 * list oneofs in docstring ([be96ebc](https://www.github.com/googleapis/python-analytics-admin/commit/be96ebc5d99e3d3ea1883ce22fafa95847825fb3))
 
-### [0.7.1](https://www.github.com/googleapis/python-analytics-admin/compare/v0.7.0...v0.7.1) (2021-10-19)
+## [0.7.1](https://www.github.com/googleapis/python-analytics-admin/compare/v0.7.0...v0.7.1) (2021-10-19)
 
 
 ### Documentation
@@ -71,7 +71,7 @@
 
 * add context manager support in client ([#146](https://www.github.com/googleapis/python-analytics-admin/issues/146)) ([f1559b6](https://www.github.com/googleapis/python-analytics-admin/commit/f1559b6074e75e453e0f3c6f32a21bfac487e562))
 
-### [0.5.2](https://www.github.com/googleapis/python-analytics-admin/compare/v0.5.1...v0.5.2) (2021-10-07)
+## [0.5.2](https://www.github.com/googleapis/python-analytics-admin/compare/v0.5.1...v0.5.2) (2021-10-07)
 
 
 ### Bug Fixes
@@ -83,7 +83,7 @@
 
 * add samples for accounts.search_change_history_events() method ([#137](https://www.github.com/googleapis/python-analytics-admin/issues/137)) ([c299b37](https://www.github.com/googleapis/python-analytics-admin/commit/c299b370c42a8684faa86f5bb5f65b3da8a2d0a8))
 
-### [0.5.1](https://www.github.com/googleapis/python-analytics-admin/compare/v0.5.0...v0.5.1) (2021-09-24)
+## [0.5.1](https://www.github.com/googleapis/python-analytics-admin/compare/v0.5.0...v0.5.1) (2021-09-24)
 
 
 ### Bug Fixes
@@ -120,7 +120,7 @@
 * rename `email_address` field of `GoogleAdsLink` type to `creator_email_address` ([2a1c5a0](https://www.github.com/googleapis/python-analytics-admin/commit/2a1c5a098503d075633222a7b926efe2d7026559))
 * rename `is_deletable` field of `ConversionEvent` type to `deletable` ([2a1c5a0](https://www.github.com/googleapis/python-analytics-admin/commit/2a1c5a098503d075633222a7b926efe2d7026559))
 
-### [0.4.3](https://www.github.com/googleapis/python-analytics-admin/compare/v0.4.2...v0.4.3) (2021-07-27)
+## [0.4.3](https://www.github.com/googleapis/python-analytics-admin/compare/v0.4.2...v0.4.3) (2021-07-27)
 
 
 ### Bug Fixes
@@ -137,14 +137,14 @@
 
 * release as 0.4.3 ([#108](https://www.github.com/googleapis/python-analytics-admin/issues/108)) ([4dd86a1](https://www.github.com/googleapis/python-analytics-admin/commit/4dd86a139ecfcdab9b1ed847fe7c76fb578ca6af))
 
-### [0.4.2](https://www.github.com/googleapis/python-analytics-admin/compare/v0.4.1...v0.4.2) (2021-07-20)
+## [0.4.2](https://www.github.com/googleapis/python-analytics-admin/compare/v0.4.1...v0.4.2) (2021-07-20)
 
 
 ### Bug Fixes
 
 * **deps:** pin 'google-{api,cloud}-core', 'google-auth' to allow 2.x versions ([#101](https://www.github.com/googleapis/python-analytics-admin/issues/101)) ([cde3379](https://www.github.com/googleapis/python-analytics-admin/commit/cde3379e9b40082f69327b46ba0acdabe520c21b))
 
-### [0.4.1](https://www.github.com/googleapis/python-analytics-admin/compare/v0.4.0...v0.4.1) (2021-06-30)
+## [0.4.1](https://www.github.com/googleapis/python-analytics-admin/compare/v0.4.0...v0.4.1) (2021-06-30)
 
 
 ### Bug Fixes
@@ -164,14 +164,14 @@
 
 * omit mention of Python 2.7 in 'CONTRIBUTING.rst' ([#1127](https://www.github.com/googleapis/python-analytics-admin/issues/1127)) ([#84](https://www.github.com/googleapis/python-analytics-admin/issues/84)) ([6ce863e](https://www.github.com/googleapis/python-analytics-admin/commit/6ce863e147dae3c1da40c27034a0ac42180c6303)), closes [#1126](https://www.github.com/googleapis/python-analytics-admin/issues/1126)
 
-### [0.3.2](https://www.github.com/googleapis/python-analytics-admin/compare/v0.3.1...v0.3.2) (2021-06-16)
+## [0.3.2](https://www.github.com/googleapis/python-analytics-admin/compare/v0.3.1...v0.3.2) (2021-06-16)
 
 
 ### Bug Fixes
 
 * **deps:** add packaging requirement ([#80](https://www.github.com/googleapis/python-analytics-admin/issues/80)) ([6d99bcc](https://www.github.com/googleapis/python-analytics-admin/commit/6d99bcc3e940e4f6bc857e7d4ede53e01537c7ec))
 
-### [0.3.1](https://www.github.com/googleapis/python-analytics-admin/compare/v0.3.0...v0.3.1) (2021-06-16)
+## [0.3.1](https://www.github.com/googleapis/python-analytics-admin/compare/v0.3.0...v0.3.1) (2021-06-16)
 
 
 ### Bug Fixes