ci(android): drop ndk.abiFilters to allow --split-per-abi

  AGP rejects ndk.abiFilters alongside the abi splits config that
  `flutter build apk --split-per-abi` enables. Drop the explicit filter
  in the Android build.gradle template; Flutter's default android-arm,
  android-arm64, android-x64 set is what we want anyway, and the CI's
  APK-renaming step already references those ABI names.

Author: danrmiller

scripts/app_config/templates/android/app/build.gradle

@@ -45,9 +45,9 @@ android {
             coreLibraryDesugaring("com.android.tools:desugar_jdk_libs:2.0.4")
         }
 
-        ndk {
-            abiFilters "x86_64","armeabi-v7a", "arm64-v8a"
-        }
+        // No ndk.abiFilters here: AGP rejects it alongside the abi splits set
+        // up by `flutter build apk --split-per-abi`. Flutter defaults to
+        // android-arm,android-arm64,android-x64 which is the same set we want.
 
 //        externalNativeBuild {
 //            cmake {