tighten up the eslint check - fail if there are more than 1 lint warn…

…ings.

this is better than handwaving them.
one warning is to be expected, and it's always the same one.
let's fail if we receive any more warnings than that.

.github/workflows/ci.yml

@@ -106,7 +106,7 @@ jobs:
 
       - name: Grunt
         if: ${{ !cancelled() }}
-        run: moodle-plugin-ci grunt --show-lint-warnings
+        run: moodle-plugin-ci grunt --max-lint-warnings 1
 
       - name: PHPUnit tests
         if: ${{ !cancelled() }}