refactor(credentials): remove unnecessary import check for coverage

Author: anubhav756

packages/toolbox-adk/src/toolbox_adk/credentials.py

@@ -16,10 +16,7 @@
 from typing import Any, Optional, List, Dict
 from enum import Enum
 
-try:
-    from google.auth import credentials as google_creds
-except ImportError:
-    google_creds = None  # pragma: no cover
+from google.auth import credentials as google_creds
 
 
 class CredentialType(Enum):