Smallest change to get android ci to pass (#2337)

Fixes #2336 2336

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [ ] I updated/added relevant documentation (doc comments with `///`).
- [x] All existing and new tests are passing.

add_to_app/prebuilt_module/android_using_prebuilt_module/app/build.gradle

@@ -6,7 +6,7 @@ android {
     compileSdkVersion 33
     defaultConfig {
         applicationId "dev.flutter.example.androidusingprebuiltmodule"
-        minSdkVersion 19
+        minSdkVersion 21
         targetSdkVersion 33
         versionCode 1
         versionName "1.0"