Fix for with-ant-design-less for next7.0 (#5263)

* Update .babelrc

babel-plugin-transform-decorators-legacy does not exist in babel 7 in replace use @babel/plugin-proposal-decorators

* Update package.json

Acording the last commit please,  test this example , will be work .

examples/with-ant-design-less/.babelrc

 {
   "presets": ["next/babel"],
   "plugins": [
-    "transform-decorators-legacy",
+    ["@babel/plugin-proposal-decorators", { "decoratorsBeforeExport": true }],
     [
       "import",
       {

examples/with-ant-design-less/package.json

@@ -17,6 +17,6 @@
   },
   "license": "ISC",
   "devDependencies": {
-    "babel-plugin-transform-decorators-legacy": "^1.3.5"
+    "@babel/plugin-proposal-decorators": "^7.1.0"
   }
 }