Fix ForTypeRepr docs and test with proper instance

rust/schema/annotations.py

@@ -1158,13 +1158,12 @@ class _:
 @annotate(ForTypeRepr)
 class _:
     """
-    A type with a higher-ranked `for` modifier. This is currently not valid Rust syntax (`for<...>` can
-    only be applied to traits to form a `TypeBound`).
+    A function pointer type with a `for` modifier.
 
     For example:
     ```rust
-    fn foo(value: for<'a> usize) {}  // DOESN'T COMPILE
-    //            ^^^^^^^^^^^^^
+    type RefOp<X> = for<'a> fn(&'a X) -> &'a X;
+    //              ^^^^^^^^^^^^^^^^^^^^^^^^^^
     ```
     """