fix: increase default retry deadline to 10 minutes (#859)

The backend API has a timeout of 4 minutes, so the default of 2 minutes was not
allowing for any retries to happen in some cases.

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Fixes #853  🦕

Author: tswast

google/cloud/bigquery/retry.py

@@ -47,7 +47,7 @@ def _should_retry(exc):
     return reason in _RETRYABLE_REASONS
 
 
-DEFAULT_RETRY = retry.Retry(predicate=_should_retry)
+DEFAULT_RETRY = retry.Retry(predicate=_should_retry, deadline=600.0)
 """The default retry object.
 
 Any method with a ``retry`` parameter will be retried automatically,