ci: update test job runner from ubuntu-20.04 to ubuntu-22.04 (#163)

ubuntu-20.04 GitHub-hosted runners are no longer available, causing the
Test job to wait indefinitely for a runner that never picks it up.
ubuntu-22.04 is the current LTS and has full runner availability.

Author: TimeToBuildBob

.github/workflows/build.yml

@@ -229,7 +229,7 @@ jobs:
 
   test:
     name: Test
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     needs: [build-rust]
     env:
       SUPPLY_TRACK: production   # used by fastlane to determine track to publish to