Run instrumented tests on x86_64 ABI-compatible host

The default was x86 for which we don't even have active device installs of the
main app in Google Play.

Not that we have any for x86_64 either, but it's "slightly closer of a step" to
arm64-8va given that ARM-based Actions runners aren't available yet.

.github/workflows/instrumented-test.yml

@@ -27,4 +27,5 @@ jobs:
       - uses: reactivecircus/[email protected]
         with:
           api-level: 29
+          arch: x86_64
           script: ./gradlew -Dorg.gradle.logging.level=quiet connectedCheck