[docs] Use @material-ui/core in the guide

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

@@ -5,8 +5,8 @@
 The bundle size of Material-UI is taken very seriously, so
 [size-limit](https://github.com/ai/size-limit) is used to prevent introducing any size regression.
 The size of the bundle is checked at each commit:
-- When importing **all the components**. This lets us spot any [unwanted bundle size increase](https://github.com/mui-org/material-ui/blob/master/.size-limit.js#L24).
-- When importing **a single component**. This lets us estimate [the overhead of our core dependencies](https://github.com/mui-org/material-ui/blob/master/.size-limit.js#L30). (styling, theming, etc.: ~20 kB gzipped)
+- When importing **all the components**. This lets us spot any [unwanted bundle size increase](https://github.com/mui-org/material-ui/blob/master/.size-limit.js#L30).
+- When importing **a single component**. This lets us estimate [the overhead of our core dependencies](https://github.com/mui-org/material-ui/blob/master/.size-limit.js#L24). (styling, theming, etc.: ~18 kB gzipped)
 
 ## How to reduce the bundle size?
 
@@ -21,7 +21,7 @@ You have couple of options to overcome this situation:
 You can import directly from `material-ui/` to avoid pulling in unused modules. For instance, instead of:
 
 ```js
-import { Button, TextField } from 'material-ui';
+import { Button, TextField } from '@material-ui/core';
 ```
 
 use:
@@ -40,7 +40,7 @@ For example, the `Tabs` component is a public module while `TabIndicator` is pri
 Another option is to keep using the shortened import like the following, but still have the size of the bundle optimized thanks to a **Babel plugin**:
 
 ```js
-import { Button, TextField } from 'material-ui';
+import { Button, TextField } from '@material-ui/core';
 ```
 
 Pick one of the following plugins: