Add support for new where clause location in associated types.

A recent Rust nightly changed it: https://github.com/rust-lang/rust/issues/89122

This allows both the old and new location.

crates/parser/src/grammar/items.rs

@@ -290,12 +290,17 @@ fn type_alias(p: &mut Parser, m: Marker) {
         generic_params::bounds(p);
     }
 
-    // test type_item_where_clause
+    // test type_item_where_clause_deprecated
     // type Foo where Foo: Copy = ();
     generic_params::opt_where_clause(p);
     if p.eat(T![=]) {
         types::type_(p);
     }
+
+    // test type_item_where_clause
+    // type Foo = () where Foo: Copy;
+    generic_params::opt_where_clause(p);
+
     p.expect(T![;]);
     m.complete(p, TYPE_ALIAS);
 }