snippetgen: streaming methods have syntax errors

[busunkim96]

Generated snippets for streaming methods have incorrect syntax:

gapic-generator-python/tests/integration/goldens/logging/samples/generated_samples/logging_generated_logging_v2_logging_service_v2_tail_log_entries_async.py

Lines 36 to 44 in dbfb45a

	# Initialize request argument(s)
	request = logging_v2.TailLogEntriesRequest(
	resource_names=['resource_names_value'],
	)
	# Make the request
	stream = await client.tail_log_entries([resource_names=['resource_names_value']])
	async for response in stream:
	print(response)