CI: Rehash environment after installing macOS dependencies

zsh requires the `rehash` command to discover newly installed commands
on the system.

.github/scripts/utils.zsh/check_macos

@@ -16,3 +16,4 @@ if (( ! ${+commands[brew]} )) {
   return 2
 }
 brew bundle --file "${SCRIPT_HOME}/.Brewfile"
+rehash