update: 升级element版本

package.json

@@ -11,7 +11,7 @@
     "version": "conventional-changelog -p angular -i changelog.md -s -r 0 && git add changelog.md"
   },
   "dependencies": {
-    "element-ui": "^2.8.2",
+    "element-ui": "^2.15.6",
     "file-saver": "^1.3.8",
     "moment": "^2.29.1",
     "tinymce": "^4.8.3",