automation: switch to us-west-2 by default

This is where the AWS account I'm running lives.

Differential Revision: https://phab.mercurial-scm.org/D6981

contrib/automation/hgautomation/cli.py

@@ -204,7 +204,7 b' def get_parser():'
     parser.add_argument(
         '--aws-region',
         help='AWS region to use',
-        default='us-west-1',
+        default='us-west-2',
     )
 
     subparsers = parser.add_subparsers()