Code style and fixes to comments

Contributes to issue CURA-5785.

plugins/PreviewStage/PreviewMenu.qml

@@ -60,7 +60,7 @@ Item
                         }
                     }
                     // Nothing was active, so just return the first one (the list is sorted by priority, so the most
-                    // important one sshould be returned)
+                    // important one should be returned)
                     return viewModel.getItem(0)
                 }