Use m1 machines for CircleCI mac builds (facebook#1092)

Summary:
Pull Request resolved: facebook#1092

Update CircleCI to use the `macos.m1.medium.gen1` resource class,
replacing the deprecated `macos.x86.medium.gen2`.

Reviewed By: dannysu

Differential Revision: D48154737

fbshipit-source-id: 4c4357bd9196e0e5f1012bdb484a8066b0eeffd9

.circleci/config.yml

@@ -39,7 +39,7 @@ workflows:
 apple_defaults: &apple_defaults
   macos:
     xcode: 13.4.1
-  resource_class: macos.x86.medium.gen2
+  resource_class: macos.m1.medium.gen1
   working_directory: ~/hermes
   environment:
     - TERM: dumb