Use Edition 2021 :pat in matches macro

This makes the macro syntax used in documentation more readable.

library/core/src/macros/mod.rs

@@ -340,9 +340,9 @@ pub macro debug_assert_matches($($arg:tt)*) {
 #[stable(feature = "matches_macro", since = "1.42.0")]
 #[cfg_attr(not(test), rustc_diagnostic_item = "matches_macro")]
 macro_rules! matches {
-    ($expression:expr, $(|)? $( $pattern:pat_param )|+ $( if $guard: expr )? $(,)?) => {
+    ($expression:expr, $pattern:pat $(if $guard:expr)? $(,)?) => {
         match $expression {
-            $( $pattern )|+ $( if $guard )? => true,
+            $pattern $(if $guard)? => true,
             _ => false
         }
     };