Homebrew install: ignore pinned formulae in `brew upgrade` (#11423)

util/install/macos.sh

@@ -9,7 +9,7 @@ _qmk_install_prepare() {
         return 1
     fi
 
-    brew update && brew upgrade
+    brew update && brew upgrade --ignore-pinned
 }
 
 _qmk_install() {