docs: fix changelog header to consistent size (#434)

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

CHANGELOG.md

@@ -11,7 +11,7 @@
 
 * Add SavedQuery CURD support ([#425](https://github.com/googleapis/python-asset/issues/425)) ([b3e5650](https://github.com/googleapis/python-asset/commit/b3e5650732e46c4c6ee7835cdfa38c1232efb3b9))
 
-### [3.8.1](https://github.com/googleapis/python-asset/compare/v3.8.0...v3.8.1) (2022-03-05)
+## [3.8.1](https://github.com/googleapis/python-asset/compare/v3.8.0...v3.8.1) (2022-03-05)
 
 
 ### Bug Fixes
@@ -36,7 +36,7 @@
 
 * add autogenerated code snippets ([8e6877d](https://github.com/googleapis/python-asset/commit/8e6877de9c5969d493e67f545b93d0059c8ca182))
 
-### [3.7.1](https://www.github.com/googleapis/python-asset/compare/v3.7.0...v3.7.1) (2021-11-02)
+## [3.7.1](https://www.github.com/googleapis/python-asset/compare/v3.7.0...v3.7.1) (2021-11-02)
 
 
 ### Bug Fixes
@@ -57,7 +57,7 @@
 
 * add context manager support in client ([#314](https://www.github.com/googleapis/python-asset/issues/314)) ([659db45](https://www.github.com/googleapis/python-asset/commit/659db456ff6cc7a09fffd83479b2b43d5905239f))
 
-### [3.6.1](https://www.github.com/googleapis/python-asset/compare/v3.6.0...v3.6.1) (2021-09-30)
+## [3.6.1](https://www.github.com/googleapis/python-asset/compare/v3.6.0...v3.6.1) (2021-09-30)
 
 
 ### Bug Fixes
@@ -114,7 +114,7 @@
 * add Samples section to CONTRIBUTING.rst ([#235](https://www.github.com/googleapis/python-asset/issues/235)) ([0d00e75](https://www.github.com/googleapis/python-asset/commit/0d00e75bf46d52beea0829b83a2df580a37491ca))
 
 
-### [3.2.1](https://www.github.com/googleapis/python-asset/compare/v3.2.0...v3.2.1) (2021-07-21)
+## [3.2.1](https://www.github.com/googleapis/python-asset/compare/v3.2.0...v3.2.1) (2021-07-21)
 
 
 ### Bug Fixes