Fix the code sample of using BigQuery with the application default credentails (#825)

* Fix the code sample of using BigQuery with the application default credentails

* Update bigquery.py

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Co-authored-by: Kristopher Overholt <[email protected]>
Co-authored-by: Joe Fernandez <[email protected]>

Author: 3 people

examples/python/snippets/tools/built-in-tools/bigquery.py

@@ -34,13 +34,10 @@
 # Define a tool configuration to block any write operations
 tool_config = BigQueryToolConfig(write_mode=WriteMode.BLOCKED)
 
-# Define a credentials config - in this example we are using application default
-# credentials
+# Uses externally-managed Application Default Credentials (ADC) by default.
+# This decouples authentication from the agent / tool lifecycle.
 # https://cloud.google.com/docs/authentication/provide-credentials-adc
-application_default_credentials, _ = google.auth.default()
-credentials_config = BigQueryCredentialsConfig(
-    credentials=application_default_credentials
-)
+credentials_config = BigQueryCredentialsConfig()
 
 # Instantiate a BigQuery toolset
 bigquery_toolset = BigQueryToolset(