Use androidx compat alert dialog

Author: TobiGr

app/src/main/java/org/schabi/newpipe/util/PermissionHelper.java

@@ -2,7 +2,6 @@
 
 import android.Manifest;
 import android.app.Activity;
-import android.app.AlertDialog;
 import android.content.ActivityNotFoundException;
 import android.content.Context;
 import android.content.Intent;
@@ -14,6 +13,7 @@
 import android.widget.Toast;
 
 import androidx.annotation.RequiresApi;
+import androidx.appcompat.app.AlertDialog;
 import androidx.core.app.ActivityCompat;
 import androidx.core.content.ContextCompat;