Enable typing in Homebrew::Upgrade

[dduugg]

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This enabled typing in the Homebrew::Upgrade module

[BrewTestBot]

Review period will end on 2023-02-15 at 19:10:57 UTC.

[dduugg]

The f here always results in a NameError here, afaitct. I believe this was a bug that was introduced in the beginning: https://github.com/Homebrew/brew/pull/12024/files#diff-338a6a0ff7eb3b254fa3b6ca7d9225e7e283521c05acbdcda7f4eb8dc996bc05R206

(You should be able to replicate this by removing the rescue and running test/cmd/install_spec.)

However: 1) it wasn't covered by tests (it seems linked_kegs is always present?), 2) it's wrapped in a bare rescue (which I would discourage, but I don't have sufficient context here to know how to better target it), and 3) the file was untyped.

formula is my best guess as to the original intent, and I've rearranged things a bit so that it's covered in tests.

cc @FnControlOption @MikeMcQuaid

[MikeMcQuaid]

Thanks again @dduugg!

[BrewTestBot]

Review period skipped due to critical label.