Fix android build min sdk version

android/app/build.gradle

@@ -47,7 +47,7 @@ android {
         applicationId "social.myportal.flutter_portal"
         // You can update the following values to match your application needs.
         // For more information, see: https://docs.flutter.dev/deployment/android#reviewing-the-build-configuration.
-        minSdkVersion 18
+        minSdkVersion 19
         targetSdkVersion flutter.targetSdkVersion
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName