Change installation methods of release-index-gen and gitlab-changelog
What does this MR do?
Updates the way how release-index-gen and gitlab-changelog are installed.
The change includes bumping release-index-gen to a fixed version without the random failure bug.
Why was this MR needed?
Are there points in the code the reviewer needs to double check?
Does this MR meet the acceptance criteria?
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Documentation created/updated 
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Added tests for this feature/bug 
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In case of conflicts with master- branch was rebased