`test_github_release_page` is broken

[NotTheEvilOne]

What happened:
PR #231 has been merged without fixing the unit tests for it. The file test-data/release_notes/github_release_notes_1877.3.md needs to be adapted.

[vivus-ignis]

This is addressed here https://github.com/gardenlinux/python-gardenlinux-lib/pull/232/files#diff-229754b063b82a663b0273f77bf3325f4b4eecc82b0e378a59799454f30911d1

[NotTheEvilOne]

This is unrelated to PR #232, maybe you can split it to a separate PR?

[vivus-ignis]

Pushed a separate PR: #237