SendKeysRowSettings: Avoid adding twice the same widgets

This fixes the following error:

    (com.github.joseexposito.touche:2): Gtk-CRITICAL **: 18:48:10.669:
    gtk_grid_attach: assertion '_gtk_widget_get_parent (child) == NULL'
    failed

src/main-view/content/row-settings/send-keys-row-settings.js

@@ -110,8 +110,9 @@ class SendKeysRowSettings extends Gtk.Grid {
     this.attach(repeatLabel, 0, 1, 1, 1);
     this.attach(this.repeatSwitch, 1, 1, 1, 1);
     this.repeatChanged(isRepeatActive);
-    this.attach(this.animationLabel, 0, 3, 1, 1);
-    this.attach(this.animationCombo, 1, 3, 1, 1);
+    // No need to add them here, added by `repeatChanged`:
+    // this.attach(this.animationLabel, 0, 3, 1, 1);
+    // this.attach(this.animationCombo, 1, 3, 1, 1);
   }
 
   repeatChanged(isRepeatActive) {