Modify workflow (#520)

Signed-off-by: mramotar <mramotar@dropbox.com>

Author: matt-ramotar

.github/workflows/check.yml

@@ -6,8 +6,6 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v2
-        with:
-          ref: ${{ github.event.pull_request.head.ref }}
       - name: Setup Gradle
         uses: gradle/gradle-build-action@v2
       - name: Run check with Gradle Wrapper