Upgrade checkout action to version 4

Author: holmeso

.github/workflows/docker_build_test.yml

@@ -20,10 +20,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Clone Cromwell
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           repository: broadinstitute/cromwell
-          token: ${{ secrets.BROADBOT_GITHUB_TOKEN }}
           path: cromwell
       - uses: sbt/setup-sbt@v1
       - uses: actions/setup-java@v4