fix trailing commas in Main.sublime-menu

.sublime/Main.sublime-menu

@@ -23,11 +23,11 @@
                                     "file": "$packages/User/MarkdownLivePreview.css",
                                     "contents": "/* See http://www.sublimetext.com/docs/3/minihtml.html#css to know which property you're able to use */\n\n$0"
                                 }
-                            },
+                            }
                         ]
-                    },
-                ],
-            },
+                    }
+                ]
+            }
         ]
     }
 ]