iam: remove extra spaces after region tag (GoogleCloudPlatform#2417)

There were a few extra spaces after the [START iam_enable_service_account] region tag.

Author: melaniedejong

iam/api-client/service_accounts.py

@@ -131,9 +131,8 @@ def disable_service_account(email):
     print("Disabled service account :" + email)
 # [END iam_disable_service_account]
 
-# [START iam_enable_service_account]
-
 
+# [START iam_enable_service_account]
 def enable_service_account(email):
     """Enables a service account."""