chore: 升级element版本

litemall-admin/package.json

@@ -28,7 +28,7 @@
     "clipboard": "1.7.1",
     "connect": "3.6.6",
     "echarts": "4.1.0",
-    "element-ui": "2.7.2",
+    "element-ui": "2.12.0",
     "file-saver": "1.3.8",
     "font-awesome": "4.7.0",
     "js-cookie": "2.2.0",