ci: drop no-op gettext link on macOS

Homebrew's gettext formula used to be keg-only, meaning brew would install it into the Cellar without linking its headers, libraries, or utilities like msgfmt anywhere on the default search paths, to avoid clashing with software that already ships its own gettext. brew link --force gettext overrode that restriction so the keg-only install became visible on the paths git's build and tests rely on.

Homebrew dropped gettext's keg-only status in 2020 (https://github.com/Homebrew/homebrew-core/pull/53489), so a fresh install now links into the prefix by itself. brew link --force against an already-linked keg has nothing left to override, and only produces a spurious "Already linked" warning in every macOS job's log.

Signed-off-by: Harald Nordgren haraldnordgren@gmail.com