Downgrade AArch64 CI builds host OS to Ubuntu 22.04

There are numerous reports of 24.04-arm host being unstable: rust-lang/rust#135867

cc davidlattimore#365

Author: mati865

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
       matrix:
         runs-on:
           - ubuntu-latest
-          - ubuntu-24.04-arm
+          - ubuntu-22.04-arm
         container:
           - 'ubuntu:22.04'
           - 'ubuntu:latest'