Rollup merge of #139157 - mejrs:never, r=Noratrieb

Remove mention of `exhaustive_patterns` from `never` docs

The example shows an exhaustive match:
```rust
#![feature(exhaustive_patterns)]
use std::str::FromStr;
let Ok(s) = String::from_str("hello");
```
But https://github.com/rust-lang/rust/issues/119612 moved this functionality to `#![feature(min_exhaustive_patterns)` and then stabilized it.

library/core/src/primitive_docs.rs

@@ -127,15 +127,13 @@ mod prim_bool {}
 /// [`Result<String, !>`] which we can unpack like this:
 ///
 /// ```
-/// #![feature(exhaustive_patterns)]
 /// use std::str::FromStr;
 /// let Ok(s) = String::from_str("hello");
 /// ```
 ///
-/// Since the [`Err`] variant contains a `!`, it can never occur. If the `exhaustive_patterns`
-/// feature is present this means we can exhaustively match on [`Result<T, !>`] by just taking the
-/// [`Ok`] variant. This illustrates another behavior of `!` - it can be used to "delete" certain
-/// enum variants from generic types like `Result`.
+/// Since the [`Err`] variant contains a `!`, it can never occur. This means we can exhaustively
+/// match on [`Result<T, !>`] by just taking the [`Ok`] variant. This illustrates another behavior
+/// of `!` - it can be used to "delete" certain enum variants from generic types like `Result`.
 ///
 /// ## Infinite loops
 ///