Fix CHANGELOG header

Prepare release version 6.2.4

Prepare release version 6.2.3

Prepare release version 6.2.2

Prepare release version 6.2.1

Merge pull request pytest-dev#8131 from bluetech/cherry-pick-release

Merge pull request pytest-dev#8130 from pytest-dev/release-6.2.0

Prepare release version 6.2.0

Prepare release version 6.1.2

Prepare release version 6.1.1

Merge pull request pytest-dev#7798 from bluetech/cherry-pick-release

Cherry-pick 6.1.0 release notes