docs: fix changelog header to consistent size (#209)

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

Author: dandhlee

packages/google-cloud-billing-budgets/CHANGELOG.md

@@ -1,5 +1,5 @@
 # Changelog
-### [1.6.1](https://github.com/googleapis/python-billingbudgets/compare/v1.6.0...v1.6.1) (2022-03-05)
+## [1.6.1](https://github.com/googleapis/python-billingbudgets/compare/v1.6.0...v1.6.1) (2022-03-05)
 
 
 ### Bug Fixes
@@ -25,7 +25,7 @@
 * add autogenerated code snippets ([5e02634](https://github.com/googleapis/python-billingbudgets/commit/5e026345b1cb9cc77359d7efd98a07ce498a7e74))
 * Formatting change from HTML to markdown; Additional clarifications ([#174](https://github.com/googleapis/python-billingbudgets/issues/174)) ([eaa109d](https://github.com/googleapis/python-billingbudgets/commit/eaa109d24a6af7ad014e8c5606c88c7432f022ff))
 
-### [1.5.1](https://www.github.com/googleapis/python-billingbudgets/compare/v1.5.0...v1.5.1) (2021-11-01)
+## [1.5.1](https://www.github.com/googleapis/python-billingbudgets/compare/v1.5.0...v1.5.1) (2021-11-01)
 
 
 ### Bug Fixes
@@ -47,21 +47,21 @@
 * add context manager support in client ([#145](https://www.github.com/googleapis/python-billingbudgets/issues/145)) ([e8f1dc0](https://www.github.com/googleapis/python-billingbudgets/commit/e8f1dc09a5b932f00bc279d8510aa5518d68b98b))
 * add trove classifier for python 3.10 ([#149](https://www.github.com/googleapis/python-billingbudgets/issues/149)) ([b75cf0c](https://www.github.com/googleapis/python-billingbudgets/commit/b75cf0ca43929d6339647aa99e02ecc6e7f25c5c))
 
-### [1.4.4](https://www.github.com/googleapis/python-billingbudgets/compare/v1.4.3...v1.4.4) (2021-10-04)
+## [1.4.4](https://www.github.com/googleapis/python-billingbudgets/compare/v1.4.3...v1.4.4) (2021-10-04)
 
 
 ### Bug Fixes
 
 * improper types in pagers generation ([47eb773](https://www.github.com/googleapis/python-billingbudgets/commit/47eb77346fe44ce803a20552347bb42c4a17e5a5))
 
-### [1.4.3](https://www.github.com/googleapis/python-billingbudgets/compare/v1.4.2...v1.4.3) (2021-09-24)
+## [1.4.3](https://www.github.com/googleapis/python-billingbudgets/compare/v1.4.2...v1.4.3) (2021-09-24)
 
 
 ### Bug Fixes
 
 * add 'dict' annotation type to 'request' ([746a7a1](https://www.github.com/googleapis/python-billingbudgets/commit/746a7a13524217f5f0562ac35b963de17bea11bf))
 
-### [1.4.2](https://www.github.com/googleapis/python-billingbudgets/compare/v1.4.1...v1.4.2) (2021-07-27)
+## [1.4.2](https://www.github.com/googleapis/python-billingbudgets/compare/v1.4.1...v1.4.2) (2021-07-27)
 
 
 ### Bug Fixes
@@ -78,7 +78,7 @@
 
 * release as 1.4.2 ([#122](https://www.github.com/googleapis/python-billingbudgets/issues/122)) ([652c0b2](https://www.github.com/googleapis/python-billingbudgets/commit/652c0b239c303369701447862d98a5aa5f109213))
 
-### [1.4.1](https://www.github.com/googleapis/python-billingbudgets/compare/v1.4.0...v1.4.1) (2021-07-20)
+## [1.4.1](https://www.github.com/googleapis/python-billingbudgets/compare/v1.4.0...v1.4.1) (2021-07-20)
 
 
 ### Bug Fixes
@@ -128,7 +128,7 @@
 
 * release 1.2.0 ([#95](https://www.github.com/googleapis/python-billingbudgets/issues/95)) ([be03be9](https://www.github.com/googleapis/python-billingbudgets/commit/be03be9af446c01ded9f7306eb376a73972de39e))
 
-### [1.1.1](https://www.github.com/googleapis/python-billingbudgets/compare/v1.1.0...v1.1.1) (2021-02-12)
+## [1.1.1](https://www.github.com/googleapis/python-billingbudgets/compare/v1.1.0...v1.1.1) (2021-02-12)
 
 
 ### Bug Fixes
@@ -142,7 +142,7 @@
 
 * add v1 ([#53](https://www.github.com/googleapis/python-billingbudgets/issues/53)) ([72ec268](https://www.github.com/googleapis/python-billingbudgets/commit/72ec26816d2ceb7217783f8a692b552fe5a2b28a))
 
-### [1.0.1](https://www.github.com/googleapis/python-billingbudgets/compare/v1.0.0...v1.0.1) (2020-08-03)
+## [1.0.1](https://www.github.com/googleapis/python-billingbudgets/compare/v1.0.0...v1.0.1) (2020-08-03)
 
 
 ### Documentation