Don't update homebrew on GitHub Actions.

QuLogic · QuLogic · commit 59c1afd9d51d · 2021-01-09T03:28:30.000-05:00
This leaves us at the mercy of whenever Actions updates the formula
database, but also prevents it from trying to update stuff in the image
that we don't want it to update.
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
@@ -91,7 +91,6 @@ jobs:
               ttf-wqy-zenhei
             ;;
           macOS)
-            brew update
             brew install ccache
             ;;
           esac
