Swap to macos.m1.medium.gen1 arm64 runner (#71)

Summary:
See title. [[context](https://fb.workplace.com/groups/osssupport/posts/24783945017894113/)]

Pull Request resolved: #71

Test Plan: CI

Reviewed By: bigfootjon

Differential Revision: D46531176

Pulled By: jacobkahn

fbshipit-source-id: 7be6442c0487a971b6ec3eb409b5df0a07a15dca

.circleci/config.yml

@@ -424,7 +424,7 @@ jobs:
   macos_arm64_wheels:
     working_directory: ~/macos_arm64_wheels
     <<: *macos_env
-    resource_class: macos.m1.large.gen1
+    resource_class: macos.m1.medium.gen1
     steps:
       - checkout
       - run:
@@ -506,15 +506,15 @@ workflows:
       - macos_clang:
           matrix:
             parameters:
-              resource_class: [macos.x86.medium.gen2, macos.m1.large.gen1]
+              resource_class: [macos.x86.medium.gen2, macos.m1.medium.gen1]
           name: "macOS (<< matrix.resource_class >>) Clang 13 no-standalone - shared + KenLM"
           use_kenlm: "ON"
           build_shared_libs: "ON"
           build_standalone: "OFF"
       - macos_clang_python:
           matrix:
             parameters:
-              resource_class: [macos.x86.medium.gen2, macos.m1.large.gen1]
+              resource_class: [macos.x86.medium.gen2, macos.m1.medium.gen1]
           name: "macOS (<< matrix.resource_class >>) Clang 13 Python + KenLM"
           use_kenlm: "ON"
       - windows_msvc: