Fix errors and warnings from brew test-bot / shellcheck (#55)

* Fix errors from shellcheck for brew test-bot.

Author: afinetooth

Diff for: .github/workflows/publish.yml

@@ -22,7 +22,7 @@ jobs:
           HOMEBREW_GITHUB_PACKAGES_TOKEN: ${{ github.token }}
           HOMEBREW_GITHUB_PACKAGES_USER: ${{ github.actor }}
           PULL_REQUEST: ${{ github.event.pull_request.number }}
-        run: brew pr-pull --debug --tap=$GITHUB_REPOSITORY $PULL_REQUEST
+        run: brew pr-pull --debug --tap="$GITHUB_REPOSITORY" "$PULL_REQUEST"
 
       - name: Push commits
         uses: Homebrew/actions/git-try-push@master
@@ -34,4 +34,4 @@ jobs:
         if: github.event.pull_request.head.repo.fork == false
         env:
           BRANCH: ${{ github.event.pull_request.head.ref }}
-        run: git push --delete origin $BRANCH
+        run: git push --delete origin "$BRANCH"

Diff for: .github/workflows/tests.yml

@@ -19,7 +19,7 @@ jobs:
 
       - name: Cache Homebrew Bundler RubyGems
         id: cache
-        uses: actions/cache@v1
+        uses: actions/cache@v3
         with:
           path: ${{ steps.set-up-homebrew.outputs.gems-path }}
           key: ${{ matrix.os }}-cache-rubygems-${{ steps.set-up-homebrew.outputs.gems-hash }}