Skip T5634 on Alpine

[geekosaur]

See #11041 and #11072. This is a cherry-pick of the Alpine test skip needed for #11072 to build, for documentation purposes.

I have decided not to link #11041 on the grounds that this is a workaround, not a fix. The actual fix may need to be made on GHC's end, though.

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Template B: This PR does not modify behaviour or interface

E.g. the PR only touches documentation or tests, does refactorings, etc.

Include the following checklist in your PR:

• Patches conform to the coding conventions.
• Is this a PR that fixes CI? If so, it will need to be backported to older cabal release branches (ask maintainers for directions).

[Mikolaj]

Thank you.