[core] Remove link to older date picker domain

Same as #38422

docs/pages/blog/2020-q1-update.md

@@ -24,7 +24,7 @@ Here are the most significant improvements since the beginning of the year:
   If you wish to make your first contribution to open source, the component has a couple of ["good first issues"](https://github.com/mui/material-ui/labels/lab%3A%20Autocomplete) that can be taken.
   If you have TypeScript expertise, the component could [benefit from it](https://github.com/mui/material-ui/issues?q=is%3Aopen+label%3A%22lab%3A+Autocomplete%22+label%3Atypescript).
 
-- 📆 We have made a first [alpha release](https://next.material-ui-pickers.dev/demo/daterangepicker) of the date range picker. It's not ready to be used in production but you can start playing. We might release some of the new features of the date picker under the upcoming Enterprise offering.
+- 📆 We have made a first [alpha release](https://github.com/mui/material-ui-pickers/releases/tag/v4.0.0-alpha.4) of the date range picker. It's not ready to be used in production but you can start playing. We might release some of the new features of the date picker under the upcoming Enterprise offering.
 
   ![date picker](/static/blog/2020-q1-update/date-picker.png)
 

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

@@ -63,7 +63,7 @@ Here are the most significant improvements since March 2020:
 </TabContext>
 ```
 
-- 📆 On the [date picker](https://next.material-ui-pickers.dev/):
+- 📆 On the [date picker](https://mui.com/x/react-date-pickers/):
 
   - A new `renderInput` API which matches that of the autocomplete component has been added.
   - The input mask UX has been improved.
@@ -112,6 +112,6 @@ These are objectives, no guarantees:
 ### Enterprise components
 
 - ⌗ Make available a first alpha version of our advanced data grid component as part of the enterprise bundle.
-  You can already [play with an early version](https://muix-preview.netlify.app/#/grid).
+  You can already play with an early version.
 - 📆 Make available a first alpha version of the date range picker as part of the enterprise bundle.
-  You can already [play with an early version](https://next.material-ui-pickers.dev/demo/daterangepicker).
+  You can already play with an early version.

docs/pages/blog/april-2019-update.md

@@ -29,7 +29,7 @@ Here are the most significant improvements in April:
 
   [![Global class names](/static/blog/april-2019-update/global-class-names.png)](/system/styles/advanced/)
 
-- 📅 We have moved material-ui-pickers to our organization: [@material-ui/pickers](https://material-ui-pickers.dev/). A big thanks to **@dmtrKovalenko** for creating and owning these date/time components.
+- 📅 We have moved material-ui-pickers to our organization: [@material-ui/pickers](https://www.npmjs.com/package/@material-ui/pickers). A big thanks to **@dmtrKovalenko** for creating and owning these date/time components.
 - 🔥 We have fixed more Strict Mode warnings, getting us closer to [Concurrent React](https://legacy.reactjs.org/blog/2018/11/27/react-16-roadmap.html#react-16x-q2-2019-the-one-with-concurrent-mode) support.
 - ♿️ We have significantly improved the keyboard behavior on the Select, Menu, Button and Tooltip components. The arrow key changes feel instantaneous. The select items can be selected with the alphabetical keys. The focus visible state is better detected.
 - 💄 We have added support for responsive font sizes. You can wrap your theme with [`responsiveFontSizes()`](/material-ui/customization/typography/#responsive-font-sizes):