Fix docstring for Indexes.get_default() to have correct return type.
Fix docstring for Indexes.get_default() to have correct return type.

lowtalker/splunk-sdk-python,kkirsche/splunk-sdk-python,splunk/splunk-sdk-python,kkirsche/splunk-sdk-python,kkirsche/splunk-sdk-python,ww9rivers/splunk-sdk-python,sullivanmatt/splunk-sdk-python,kkirsche/splunk-sdk-python,splunk/splunk-sdk-python