fixed if let guards documentation

Author: Kivooeo

src/expressions/match-expr.md

@@ -154,7 +154,7 @@ Moreover, by holding a shared reference while evaluating the guard, mutation ins
 
 r[expr.match.if.let.guard]
 ## If Let Guards
-Match arms can include `if let` guards to allow conditional pattern matching within the guard clause. This feature is currently unstable and requires the `#![feature(if_let_guard)]` attribute. It is tracked in issue [#51114](https://github.com/rust-lang/rust/issues/51114).
+Match arms can include `if let` guards to allow conditional pattern matching within the guard clause. This feature is currently unstable and requires the attribute. It is tracked in issue [#51114](https://github.com/rust-lang/rust/issues/51114).
 
 r[expr.match.if.let.guard.syntax]
 ```rust