test(sidekick): enable codecov

Author: coryan

codecov.yml

@@ -20,4 +20,4 @@ coverage:
         if_ci_failed: error # Set the CI status to 'error' if coverage conditions are not met
 # TODO(https://github.com/googleapis/librarian/issues/1543): restore to 80%
 ignore:
-  - internal/sidekick
+  - internal/sidekick/internal/sample