pin bundler until we are ready to upgrade

Author: jsonbailey

.github/actions/setup/action.yml

@@ -15,6 +15,7 @@ runs:
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ inputs.version }}
+        bundler: 2
 
     - name: Install dependencies
       if: ${{ inputs.install-dependencies == 'true' }}