Update feature docs for no implicit features in 2024

[epage]

See https://doc.rust-lang.org/cargo/reference/features.html

[linyihai]

I was going to update the documentation and wasn't sure if it was a good time.

If anyone is confused by this behavior, please leave a comment here and I will try to update it

[epage]

We need to come to a conclusion on #14016 first.

[epage]

As the feature has been reverted, I'm closing this