Pin AWS CLI to work around S3Proxy limitation (#2633)

Also specify architecture to allow future ARM64 CI to work.

.github/workflows/ci.yml

@@ -139,7 +139,8 @@ jobs:
       - name: Install awscli2
         run: |
           cd /tmp
-          curl "https://awscli.amazonaws.com/AWSCLIV2.pkg" -o "AWSCLIV2.pkg"
+          # TODO: pin version to work around https://github.com/gaul/s3proxy/issues/760
+          curl "https://awscli.amazonaws.com/AWSCLIV2-2.22.35.pkg" -o "AWSCLIV2.pkg"
           sudo installer -pkg AWSCLIV2.pkg -target /
 
       - name: Build