chore(sample-expo): bump pins to beta.23 and fix run:android variant flag

- exact @cpp.js/* pins 2.0.0-beta.21 -> 2.0.0-beta.23 (clean registry install
  verified end-to-end: prebuild + android/ios builds + maestro on both)
- expo run:android takes --variant, not the iOS-only --configuration flag

Author: bugra9