refactor: Move bearer_token_credentials to top-level import

grpcutil is bundled with authzed-py and always available, so the
inline import inside the use_tls branch is unnecessary.

Author: sohanmaheshwar

langchain_spicedb/core.py

@@ -20,7 +20,7 @@
     ObjectReference,
     SubjectReference,
 )
-from grpcutil import insecure_bearer_token_credentials
+from grpcutil import bearer_token_credentials, insecure_bearer_token_credentials
 
 
 @dataclass
@@ -103,8 +103,6 @@ def __init__(
         self.use_tls = use_tls
 
         if use_tls:
-            from grpcutil import bearer_token_credentials
-
             self._credentials = bearer_token_credentials(spicedb_token)
         else:
             self._credentials = insecure_bearer_token_credentials(spicedb_token)