[docs] Remove outdated references to the @next release (#16428)

* (docs) update links by removing @next, english only

* (doc) remove @next in url for /core reference

* revert translations

* fix @material-ui/styles@next

docs/src/modules/components/HomeSteps.js

@@ -115,14 +115,14 @@ function HomeSteps(props) {
             className={classes.markdownElement}
             text={`
   \`\`\`sh
-  $ npm install @material-ui/core@next
+  $ npm install @material-ui/core
   \`\`\`
                 `}
           />
           <Link
             variant="subtitle1"
             color="inherit"
-            href="https://github.com/mui-org/material-ui/tree/master/examples/cdn-next"
+            href="https://github.com/mui-org/material-ui/tree/master/examples/cdn"
             gutterBottom
           >
             {t('cdn')}

docs/src/pages/guides/migration-v3/migration-v3.md

@@ -36,11 +36,11 @@ You need to update your `package.json` to use the latest version of Material-UI.
 Or run
 
 ```sh
-npm install @material-ui/core@next
+npm install @material-ui/core
 
 or
 
-yarn add @material-ui/core@next
+yarn add @material-ui/core
 ```
 
 ### Update React version
@@ -61,11 +61,11 @@ If you were previously using `@material-ui/styles` with v3 you need to update yo
 Or run
 
 ```sh
-npm install @material-ui/styles@next
+npm install @material-ui/styles
 
 or
 
-yarn add @material-ui/styles@next
+yarn add @material-ui/styles
 ```
 
 ## Handling breaking changes
@@ -143,7 +143,7 @@ yarn add @material-ui/styles@next
     },
   }
   ```
-  
+
   *Tip: you can provide more than 1 argument: `theme.spacing(1, 2) // = '8px 16px'`*.
 
   You can use [the migration helper](https://github.com/mui-org/material-ui/tree/master/packages/material-ui-codemod/README.md#theme-spacing-api) on your project to make this smoother.
@@ -170,7 +170,7 @@ yarn add @material-ui/styles@next
 
 ### TypeScript
 
-#### `value` type 
+#### `value` type
 
 Normalized `value` prop type for input components to use `unknown`. This affects
 `InputBase`, `NativeSelect`, `OutlinedInput`, `Radio`, `RadioGroup`, `Select`, `SelectInput`, `Switch`, `TextArea`,  and `TextField`.

docs/src/pages/guides/minimizing-bundle-size/minimizing-bundle-size.md

@@ -102,7 +102,7 @@ Pick one of the following plugins:
 The package published on npm is **transpiled**, with [Babel](https://github.com/babel/babel), to take into account the [supported platforms](/getting-started/supported-platforms/).
 
 We also publish a second version of the components.
-You can find this version under the [`/es` folder](https://unpkg.com/@material-ui/core@next/es/).
+You can find this version under the [`/es` folder](https://unpkg.com/@material-ui/core/es/).
 All the non-official syntax is transpiled to the [ECMA-262 standard](https://www.ecma-international.org/publications/standards/Ecma-262.htm), nothing more.
 This can be used to make separate bundles targeting different browsers.
 Older browsers will require more JavaScript features to be transpiled,