Only run pytest pre-commit hook when files in monkey/ are modified

.pre-commit-config.yaml

@@ -39,7 +39,5 @@ repos:
         name: pytest
         entry: bash -c "cd monkey && pytest"
         language: system
-        pass_filenames: false
-        # alternatively you could `types: [python]` so it only runs when python files change
-        # though tests might be invalidated if you were to say change a data file
-        always_run: true
+        files: "monkey/"
+        exclude: "monkey/monkey_island/cc/ui"