unit tests: don't build & start unneeded services (#3992)

* Update unit-tests.yml

Author: valentijnscholten

.github/workflows/unit-tests.yml

@@ -67,7 +67,7 @@ jobs:
 
       # phased startup so we can use the exit code from unit test container
       - name: Start MySQL
-        run: docker-compose up -d
+        run: docker-compose up --no-deps -d mysql
 
       # no celery or initializer needed for unit tests
       - name: Unit tests