[website] Remove legacy redirect
[website] Remove legacy redirect

https://github.com/mui/mui-x/pull/5594 is merged and in production
we do no longer need this rule. Now each subapps are clearly isolated
under the mui.com TLD. This keep the use of subdomain to its minimum
which help with SEO. This might also help us for docs versioning in
the future. When MUI Core, MUI X, and MUI Toolpad have different
versions, how do we host them?

mui-org/material-ui,mui-org/material-ui,mui-org/material-ui