formulae: remove duplicate aliases/renames

[ZhongRuoyu]

• Have you followed the guidelines for contributing?
• Have you ensured that your commits follow the commit style guide?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with HOMEBREW_NO_INSTALL_FROM_API=1 brew install --build-from-source <formula>, where <formula> is the name of the formula you're submitting?
• Is your test running fine brew test <formula>, where <formula> is the name of the formula you're submitting?
• Does your build pass brew audit --strict <formula> (after doing HOMEBREW_NO_INSTALL_FROM_API=1 brew install --build-from-source <formula>)? If this is a new formula, does it pass brew audit --new <formula>?

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Companion to Homebrew/brew#16622. I've checked all these formulae:

• For gnupg2, qt5, and pyqt5: the rename and the alias were added separately. I removed the aliases in favour of the formula_renames.json entries.
• For linux-headers: the formula_renames.json entry points to linux-headers@4.4 but the alias points to linux-headers@5.15. I removed the formula_renames.json entry to preserve the current behaviour (linux-headers points to 5.15).
• For the rest of them, the commit that renamed the formula also introduced an alias with the old name. For these formulae, I also removed the aliases in favour of the entries present in formula_renames.json.

[p-linnane]

Great work!

[reitermarkus]

Thanks!