Update upgrade-guide.md

[CamilleDrapier]

Update the minimum required NodeJs version reminder, based on the previous occurrence

What kind of change does this PR introduce?

• Bugfix
• Feature
• Documentation
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change?

• Yes
• No

The PR fulfills these requirements:

• It's submitted to the dev branch (or v[X] branch)
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix: #xxx[,#xxx], where "xxx" is the issue number)
• It's been tested on a Cordova (iOS, Android) app
• It's been tested on an Electron app
• Any necessary documentation has been added or updated in the docs or explained in the PR's description.

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to start a new feature discussion first and wait for approval before working on it)

Other information:

[rstoenescu]

Hi,

The min node version is 16 though. Did you encounter issues with 16?

[CamilleDrapier]

Hi,

I have not tried running the dev version of Quasar with Node 16. I thought this was a typo as it is written above that the (new) minimum version will change to 18.12.
But if I misunderstood this, let's close this PR, and I'm sorry for taking your time.