Remove duplicate test

This test was originally unique, but we accidentally duplicated it with
tests now in subtype.rs. Further, when attempting to fix PR comments on
this test, we actually fixed them on the other tests.

Co-authored-by: David Ross <daboross@daboross.net>

Author: 2 people

tests/test/unify.rs

@@ -427,19 +427,3 @@ fn quantified_types() {
         }
     }
 }
-
-#[test]
-fn subtype() {
-    test! {
-        program {
-            fn foo<'a>(a: &'a (), b: &'a ());
-            fn bar<'a, 'b>(a: &'a (), b: &'b ());
-        }
-
-        goal {
-            Subtype(for<'a> fn(&'a (), &'a ()), for<'a, 'b> fn(&'a (), &'b ()))
-        } yields {
-            "Unique"
-        }
-    }
-}