Enable broken symlink check in pull_request.yml (#23)

Author: MaxDesiatov

.github/workflows/pull_request.yml

@@ -20,5 +20,5 @@ jobs:
       api_breakage_check_enabled: false
       unacceptable_language_check_enabled: true
       license_header_check_enabled: false
-      broken_symlink_check_enabled: false
+      broken_symlink_check_enabled: true
       format_check_enabled: false