Remove the "Release cycle" from Contribute page

Those links are really specific to the release-manager and should be linked from the [https://tails.boum.org/contribute/working_together/roles/release_manager/ release manager page] and removed from the general Contribute page, except the “manual test suite” maybe, in which case it could be added to the tools for contributors.

Related issues

Is duplicate of #7047 (closed)

Original created by @BitingBird on 7211 (Redmine)

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