.drone.yml: Handle changes in submodule remote

We need to run "git submodule sync" in case we picked up a submodule
remote change when merging master into this branch when running the CI.

Author: smarter

.drone.yml

@@ -49,6 +49,7 @@ steps:
   depends_on: [ clone ]
   commands:
   - cp -R . /tmp/3/ && cd /tmp/3/
+  - git submodule sync
   - git submodule update --init --recursive --jobs 7
   - ./project/scripts/sbt community-build/test