Update `n` standard track state (#5881)
Update `n` standard track state (#5881)

As de-facto standard, compatible with every known JS engine, and as [Stage 3](https://github.com/tc39/proposals#stage-3) TC39 [proposal](https://github.com/tc39/proposal-regexp-legacy-features), the `RegExp.$n` feature should stop warning users about being not standard, as it's one of the few de-facto standard JS features we have since about ever (see every browser, and Node, support the `n` feature, and the Stage 3 proposal is not going to change that, actually is going to ufficialize its usage).
chrisdavidmills/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data,mdn/browser-compat-data