chore: raise min version in example app

Author: yardexx

example/android/app/build.gradle

@@ -44,7 +44,7 @@ android {
         // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
         applicationId "com.aheaditec.freerasp_example"
         // Talsec library needs higher version than default (16)
-        minSdkVersion 23
+        minSdkVersion flutter.minSdkVersion
         targetSdkVersion flutter.targetSdkVersion
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName