automation: use m6i instances

This instance type is much, much faster than t3 and can perform
tasks much quicker.

Differential Revision: https://phab.mercurial-scm.org/D12131

contrib/automation/hgautomation/aws.py

@@ -1157,7 +1157,7 b' def ensure_windows_dev_ami('
         ],
         'ImageId': image.id,
         'InstanceInitiatedShutdownBehavior': 'stop',
-        'InstanceType': 't3.medium',
+        'InstanceType': 'm6i.large',
         'KeyName': '%sautomation' % prefix,
         'MaxCount': 1,
         'MinCount': 1,

contrib/automation/hgautomation/cli.py

@@ -151,7 +151,7 b' def build_all_windows_packages('
     image = aws.ensure_windows_dev_ami(c, base_image_name=base_image_name)
     DIST_PATH.mkdir(exist_ok=True)
 
-    with aws.temporary_windows_dev_instances(c, image, 't3.medium') as insts:
+    with aws.temporary_windows_dev_instances(c, image, 'm6i.large') as insts:
         instance = insts[0]
 
         winrm_client = instance.winrm_client
@@ -496,7 +496,7 b' def get_parser():'
     sp.add_argument(
         '--instance-type',
         help='EC2 instance type to use',
-        default='t3.medium',
+        default='m6i.large',
     )
     sp.add_argument(
         '--python-version',