Use workflow-kotlin-test-runner-ubuntu-4core to unflake

Updates our GHA config to take advantage of the runner that was created to unflake Workflow's integration tests, for the same reason.

.github/workflows/android.yml

@@ -1,16 +1,14 @@
 name: Android CI
 
-on:
-  push:
-    branches: [ main ]
-  # Build on all pull requests, regardless of target.
-  pull_request:
+on :
+  pull_request :
+  merge_group :
 
 jobs:
   build:
     strategy:
       fail-fast: false
-    runs-on: ubuntu-latest
+    runs-on : workflow-kotlin-test-runner-ubuntu-4core
     steps:
     - uses: actions/checkout@v2
     - name: set up JDK 17
@@ -22,7 +20,7 @@ jobs:
 
   instrumentation-tests:
     name: Instrumentation tests
-    runs-on: macos-latest
+    runs-on : workflow-kotlin-test-runner-ubuntu-4core
     timeout-minutes: 30
     strategy:
       # Allow tests to continue on other devices if they fail on one device.