chore: bump less to version 3.0

angular/angular-cli#10430 has been fixed and shipped since @angular/cli 6.2.0.

It is unecessary to lock less at version 2

Author: 黄俊亮

docs/customize-theme.en-US.md

@@ -17,14 +17,10 @@ We are using [Less](http://lesscss.org/) as the development language for styling
 
 Run `ng add ng-zorro-antd --theme`，then modified the file `src/theme.less`.
 
-> Note: `ng add ng-zorro-antd --theme` will [downgrade](https://github.com/angular/angular-cli/issues/10430) the version of `less` to `2.7`.
-
 ### Without schematics
 
 Create a standalone less file named `theme.less` in `src` folder, and add the path of it to the list of `styles` in `angular.json` file.
 
-> Note: You have to [downgrade](https://github.com/angular/angular-cli/issues/10430) the version of `less` to `2.7`.
-
 ```json
 ...
   "styles": [

docs/customize-theme.zh-CN.md

@@ -16,14 +16,10 @@ Ant Design 的样式使用了 [Less](http://lesscss.org/) 作为开发语言，
 
 在初始化项目时 `ng add ng-zorro-antd --theme` 即可自动配置好自定义主题的相关文件，修改 `src/theme.less` 文件内容就可以自定义主题。
 
-> 注意：使用 `ng add ng-zorro-antd --theme` 时会[自动](https://github.com/angular/angular-cli/issues/10430)降级 `less` 到 `2.7` 版本
-
 ### 手动修改
 
 在 `src` 目录下建立一个单独的 `theme.less` 文件，在 `angular.json` 文件的 `styles` 列表加入该文件
 
-> 注意：由于 `less` 在 `3.0` 以上版本默认禁用了 `javascriptEnabled`，需要手动降级 `less` 到 `2.7` 版本
-
 ```json
 ...
   "styles": [

package.json

@@ -80,7 +80,7 @@
     "karma-coverage-istanbul-reporter": "~1.4.2",
     "karma-jasmine": "~1.1.1",
     "karma-jasmine-html-reporter": "^0.2.2",
-    "less": "^2.7.3",
+    "less": "^3.0.0",
     "less-plugin-clean-css": "^1.5.1",
     "marked": "^0.3.6",
     "ng-packagr": "^4.0.0",

schematics/ng-add/index.ts

@@ -21,7 +21,7 @@ import { Schema } from './schema';
 import schematicsFixIcon from '../fix-icon/index';
 
 const ADD_CONFIG = {
-  LESS_VERSION       : '^2.7.3',
+  LESS_VERSION       : '^3.0.0',
   CUSTOM_THEME_PATH  : 'src/theme.less',
   COMPILED_THEME_PATH: 'node_modules/ng-zorro-antd/ng-zorro-antd.min.css',
   BOOT_PAGE_PATH     : 'src/app/app.component.html',