CI: remove cabal-head before updating it (fix #10537)

[ulysses4ever]

(fix #10537)

I experimented on my fork, and it did successfully removed the old prerelease and created a new one.

Disregard the messy commit history: it will be squashed.

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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.
• [N/A] Is this a PR that fixes CI? If so, it will need to be backported to older cabal release branches (ask maintainers for directions).