Use correct command to run tests in CI

Author: ksassnowski

.github/workflows/run-tests.yml

@@ -38,4 +38,4 @@ jobs:
           composer update --${{ matrix.dependency-version }} --prefer-dist --no-interaction --no-suggest
 
       - name: Execute tests
-        run: vendor/bin/phpunit
+        run: vendor/bin/pest