Revert "Temporarily re-add Android 5 support (#2925)"

This reverts commit 37e6782032.

.github/workflows/android.yml

@@ -50,10 +50,10 @@ jobs:
           echo 'KERNEL=="kvm", GROUP="kvm", MODE="0666", OPTIONS+="static_node=kvm"' | sudo tee /etc/udev/rules.d/99-kvm4all.rules
           sudo udevadm control --reload-rules
           sudo udevadm trigger --name-match=kvm
-      - name: Run instrumented tests (API 21)
+      - name: Run instrumented tests (API 23)
         uses: ReactiveCircus/android-emulator-runner@v2
         with:
-          api-level: 21
+          api-level: 23
           arch: x86_64
           script: ./gradlew connected${{ matrix.flavor }}DebugAndroidTest
       - name: Run instrumented tests (API 35)