update dialog

app/src/main/java/com/geeksville/mesh/MainActivity.kt

@@ -27,7 +27,6 @@ import android.view.View
 import android.widget.TextView
 import android.widget.Toast
 import androidx.activity.viewModels
-import androidx.appcompat.app.AlertDialog
 import androidx.appcompat.app.AppCompatActivity
 import androidx.appcompat.app.AppCompatDelegate
 import androidx.appcompat.widget.Toolbar
@@ -1184,7 +1183,7 @@ class MainActivity : AppCompatActivity(), Logging,
     private fun chooseThemeDialog() {
 
         /// Prepare dialog and its items
-        val builder = AlertDialog.Builder(this)
+        val builder = MaterialAlertDialogBuilder(this)
         builder.setTitle(getString(R.string.choose_theme_title))
 
         val styles = arrayOf(