Fixing .kt regex

[adrinr]

Changing the regex pattern to ensure we only replace lines starting with package . Without this, we are replacing code like the following:

class MainActivity: FlutterActivity() {
       override fun configureFlutterEngine(@NonNull flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)

        val applicationInfo = packageManager.getApplicationInfo(packageName, PackageManager.GET_META_DATA)
        ...
    }
}

as it will replace the line after packageManager... for the new package name