Fix mutation reporting, make it less verbose (#964)

Co-authored-by: Matthew Grasmick <[email protected]>

.github/workflows/mutation.yml

@@ -29,7 +29,8 @@ jobs:
         if: github.event_name == 'pull_request'
         run: |
           git fetch --depth=1 origin $GITHUB_BASE_REF
-          php build/infection.phar -j8 --git-diff-filter=AM --git-diff-base=origin/$GITHUB_BASE_REF --only-covered
+          # Explicitly specify GitHub logger since our Stryker reporting will otherwise disable it.
+          php build/infection.phar -j8 --git-diff-lines --git-diff-base=origin/$GITHUB_BASE_REF --logger-github --only-covered
 
       - name: Run Infection for all files
         if: github.event_name == 'push'