EXP: [CI] Remove brew update

[pitrou]

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[github-actions]

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[pitrou]

There's a lot of variation in runtime between individual builds, but overall this doesn't seem to make the "Install dependencies" step notably faster. @kou

[pitrou]

The occasional crash on ARM64 macOS GLib & Ruby is probably unrelated (is it tracked somewhere?).

[raulcd]

The occasional crash on ARM64 macOS GLib & Ruby is probably unrelated (is it tracked somewhere?).

Yes, it is tracked here:

• [GLib][Ruby] ci/scripts/c_glib_test.sh fails consistently on new macos-26-arm64 #50302

[kou]

Sorry...