update loading-button links

docs/pages/blog/2020-q2-update.md

@@ -27,7 +27,7 @@ Here are the most significant improvements since March 2020:
 
   Adobe XD and Framer support are also up for consideration if they attract a significant audience, but not until we've polished the Sketch and Figma assets.
 
-- 🔄 `LoadingButton` – [a new component in the lab](https://mui.com/material-ui/react-button/#loading-button). This work is influenced by the [concurrent UI patterns](https://17.reactjs.org/docs/concurrent-mode-patterns.html) presented by the React team.
+- 🔄 `LoadingButton` – [a new component in the lab](https://v5.mui.com/material-ui/react-button/#loading-button). This work is influenced by the [concurrent UI patterns](https://17.reactjs.org/docs/concurrent-mode-patterns.html) presented by the React team.
 
   <img src="/static/blog/2020-q2-update/loading.gif" alt="loading" style="margin-bottom: 24px;" />
 

docs/pages/blog/2020.md

@@ -46,7 +46,7 @@ We have achieved most of what we could have hoped for.
   - [Alert](https://v4.mui.com/components/alert/)
   - [DataGrid](https://v4.mui.com/components/data-grid/)
   - [DatePicker](https://v4.mui.com/components/pickers/)
-  - [LoadingButton](https://mui.com/material-ui/react-button/#loading-button)
+  - [LoadingButton](https://v5.mui.com/material-ui/react-button/#loading-button)
   - [Timeline](https://v4.mui.com/components/timeline/)
   - [FocusTrap](https://mui.com/base-ui/react-focus-trap/)
 - We have fixed most of the issues with the [Autocomplete](https://v4.mui.com/components/autocomplete/). We have received an overwhelming interest in the component. It was impressive to see.