Fix mui date picker and time picker examples

specify stackblitz dependency on `@mui/x-date-pickers` for latest release of major version 5 instead of using `latest` which used incompatible version 6

Author: danielwarke

packages/react-renderer-demo/src/stackblitz-templates/mui-templates.js

@@ -73,7 +73,7 @@ export const dependencies = {
   '@data-driven-forms/mui-component-mapper': 'latest',
   '@data-driven-forms/common': 'latest',
   '@mui/icons-material': 'latest',
-  '@mui/x-date-pickers': 'latest',
+  '@mui/x-date-pickers': '^5.0.20',
   '@mui/material': 'latest',
   'prop-types': 'latest',
 };