GitHub: Fix wildcard expression

It seems that this was interpreted by the shell already and
resolved to something different than what Mocha made of it
under the condition that there were actually subdirectories
with tests.

.github/workflows/mocha-test.yaml

@@ -42,7 +42,7 @@ jobs:
 
       - name: Run Mocha Tests
         id: mocha-tests
-        run: npx mocha --reporter mocha-ctrf-json-reporter --reporter-options outputDir=. tests/**/*.test.ts
+        run: npx mocha --reporter mocha-ctrf-json-reporter --reporter-options outputDir=. 'tests/**/*.test.ts'
 
       - name: Generate CTRF annotations
         id: ctrf-annotations