fix: Reduce logging spam for MCP tools without authentication

Users were getting spammed with this log even though their tools didn't require authentication. To fix, reduce the log level to DEBUG so that it doesn't show up by default.

Co-authored-by: Kathy Wu <[email protected]>
PiperOrigin-RevId: 828161281

Author: wukath

src/google/adk/tools/base_authenticated_tool.py

@@ -69,10 +69,9 @@ def __init__(
     if auth_config and auth_config.auth_scheme:
       self._credentials_manager = CredentialManager(auth_config=auth_config)
     else:
-      logger.warning(
-          "auth_config or auth_config.auth_scheme is missing. Will skip"
-          " authentication.Using FunctionTool instead if authentication is not"
-          " required."
+      logger.debug(
+          "auth_config or auth_config.auth_scheme is missing, so authentication"
+          " will be skipped."
       )
       self._credentials_manager = None
     self._response_for_auth_required = response_for_auth_required