fix: names of Sass and Less (#2384)

* Sass, not SASS

* Update cssPreprocessors.spec.js

packages/@vue/cli/lib/promptModules/__tests__/cssPreprocessors.spec.js

@@ -14,7 +14,7 @@ test('CSS pre-processor ', async () => {
     },
     {
       message: 'Pick a CSS pre-processor',
-      choices: ['SASS', 'LESS', 'Stylus'],
+      choices: ['Sass', 'Less', 'Stylus'],
       choose: 0
     }
   ]

packages/@vue/cli/lib/promptModules/cssPreprocessors.js

@@ -2,7 +2,7 @@ module.exports = cli => {
   cli.injectFeature({
     name: 'CSS Pre-processors',
     value: 'css-preprocessor',
-    description: 'Add support for CSS pre-processors like SASS, Less or Stylus',
+    description: 'Add support for CSS pre-processors like Sass, Less or Stylus',
     link: 'https://cli.vuejs.org/guide/css.html'
   })
 
@@ -16,11 +16,11 @@ module.exports = cli => {
     description: `${notice}.`,
     choices: [
       {
-        name: 'SCSS/SASS',
+        name: 'Sass/SCSS',
         value: 'sass'
       },
       {
-        name: 'LESS',
+        name: 'Less',
         value: 'less'
       },
       {