v9.0.0
[material-ui][docs] Fix sentence in the All components page (#42336)
[internal] Prepare libraries for v9 stable release (#48206)
[code-infra] Setup workflow to publish internal packages (#47952)
[docs] Fix HTML validation errors (#48107)
[website] Update wording for React PDF Kit gold sponsor (#47931)
[docs-infra] Resolve a few 301s in our docs (#47746)
[docs] Polish upgrade-to-v9 doc (#48218)
[core] Remove GridLegacy component (#47956)