Upgrade Doc: Note to remove @types/next (#7830)
Upgrade Doc: Note to remove @types/next (#7830)

* [doc] Add Uninstall @types/next in Upgrading Doc

* Apply suggestions from code review

Co-Authored-By: Tim Neutkens <5ee0edb9e2229c0838f1959779f1949031de0123@timneutkens.nl>

* Update UPGRADING.md

* Update UPGRADING.md

azukaru/next.js,azukaru/next.js,flybayer/next.js,JeromeFitz/next.js,zeit/next.js,flybayer/next.js,BlancheXu/test,flybayer/next.js,zeit/next.js,azukaru/next.js,BlancheXu/test,zeit/next.js,JeromeFitz/next.js,azukaru/next.js,JeromeFitz/next.js,flybayer/next.js,JeromeFitz/next.js,BlancheXu/test