gai: remove typo from test file, and add a reference id

Author: tshepang

tests/ui/const-generics/generic_arg_infer/parend_infer.rs renamed to tests/ui/const-generics/generic_arg_infer/paren_infer.rs

@@ -1,4 +1,5 @@
 //@ check-pass
+//@ reference: items.generics.const.inferred
 
 struct Foo<const N: usize>;