remove stale entries from rules.json

[pq]

I'd like to remove a few things from our generated json descriptions of lint rules (https://github.com/dart-lang/linter/blob/gh-pages/lints/machine/rules.json).

Specifically, I'd like to remove:

• "maturity" (now state)
• "sinceLinter" (see: stop documenting "linter version" #59174)

@parlough, @devoncarew: do you have any idea who (if anyone) is using this file?

(I feel like I put this together for @csells a while back but can't recall how it's use has evolved...)

[devoncarew]

From dart-lang/lints, we're using name and description (and may end up using hasFix).

[parlough]

We currently use it to generate https://dart.dev/tools/linter-rules but I imagine that might change in the future.

However, we don't use maturity or sinceLinter anymore, so those should be safe to remove for dart.dev :)

Thanks for checking!

[csells]

no tools I know of use either of those two field, @pq

[devoncarew]

Hi - this issue just got re-pinged due to the repo transfer (dart-lang/linter#5127).