Fix android touch events for Unity 6000.

[timbotimbo]

Description

Touch input is currently broken when using flutter_embed_unity_6000_0_android.
Both for the new and old input system and independent of different Flutter or Unity versions.

This was reported in #44.

The existing touch override had to be removed from onTouchEvent to support Unity 6000.
I moved it to dispatchTouchEvent, just like I did in the old flutter+unity plugin.

It works fine in the other plugin, but somehow I forgot to update the super. calls properly for this plugin.

  // UnityPlayerSingleton.kt  flutter_embed_unity_2022_3_android
    override fun onTouchEvent(motionEvent: MotionEvent): Boolean {
        ...
        return super.onTouchEvent(motionEvent)
    }

     // CustomFrameLayout.kt  flutter_embed_unity_6000_0_android
    override fun dispatchTouchEvent(motionEvent: MotionEvent): Boolean {       
        ...
        return super.onTouchEvent(motionEvent)  // <---- Current version.
        return super.dispatchTouchEvent(motionEvent)  // <---- Should have been this.
    }

Fix

Simply updating the super calls to dispatchTouchEvent makes touch input work again.