Revert "ci: update emulator to Android 12"

This reverts commit c409f29.

Author: agonper

ci-tools/wait-for-emulator.sh

@@ -1,10 +1,10 @@
 #!/usr/bin/env bash
 
 # Install AVD files
-echo "y" | $ANDROID_HOME/cmdline-tools/latest/bin/sdkmanager --install 'system-images;android-31;google_apis;x86'
+echo "y" | $ANDROID_HOME/cmdline-tools/latest/bin/sdkmanager --install 'system-images;android-30;google_apis;x86'
 
 # Create emulator
-echo "no" | $ANDROID_HOME/cmdline-tools/latest/bin/avdmanager create avd -n xamarin_android_emulator -k 'system-images;android-31;google_apis;x86' --force
+echo "no" | $ANDROID_HOME/cmdline-tools/latest/bin/avdmanager create avd -n xamarin_android_emulator -k 'system-images;android-30;google_apis;x86' --force
 
 $ANDROID_HOME/emulator/emulator -list-avds