Make code fragment in the issue/MR description expandable

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This is very hard to work with issue where you need to scroll 10 screens to read it. Example https://gitlab.com/gitlab-org/gitlab-ce/issues/24032

That would be much easier if output of rake gitlab:check had Expand/Collapse buttons.

/cc @dzaporozhets @smcgivern @DouweM

Edited by 🤖 GitLab Bot 🤖