Fix failing test

For some reason, adding some text to match against makes this test pass.
Before, when it was *more* general, it was failing!

This seems very likely to be a bug in htmldocck, which I'm going to
investigate.

src/test/rustdoc/intra-doc/assoc-reexport-super.rs

@@ -14,7 +14,7 @@ pub use generated::MyNewType;
 mod prelude {
     impl super::MyNewType {
         /// An alias for [`Self::FOO`].
-        // @has 'foo/struct.MyNewType.html' '//a[@href="struct.MyNewType.html#associatedconstant.FOO"]'
+        // @has 'foo/struct.MyNewType.html' '//a[@href="struct.MyNewType.html#associatedconstant.FOO"]' 'Self::FOO'
         pub const FOO2: Self = Self::FOO;
     }
 }