Don't allow failing actions to be merged

Author: tijmenbruggeman

.github/workflows/check-test.yml

@@ -12,7 +12,6 @@ jobs:
   check:
     runs-on: ubuntu-latest
     timeout-minutes: 10
-    continue-on-error: true # We haven't solved all formatting issues yet.
     strategy:
       matrix:
         php: ['7.4']