ci: Fix eslint job

eslint requires a file/directory, and will fail when the parameter
is not specified. Unfortunately it only indicates the failure by
printing its help output, but not via its return value, so our test
still completes successfully.

https://gitlab.gnome.org/GNOME/gnome-shell-extensions/merge_requests/105

.gitlab-ci.yml

@@ -24,7 +24,7 @@ eslint:
   image: registry.gitlab.gnome.org/gnome/gnome-shell/extension-ci:v1
   stage: source_check
   script:
-    - eslint -o $LINT_LOG --no-color || { cat $LINT_LOG; false; }
+    - eslint -o $LINT_LOG extensions --no-color || { cat $LINT_LOG; false; }
   <<: *only_default
   artifacts:
     paths: