[ty] highlight special type syntax in hovers as xml (#22005)

## Summary

These types look better rendered as XML than python

## Test Plan

<img width="532" height="299" alt="Screenshot 2025-12-16 at 8 40 56 AM"
src="https://github.com/user-attachments/assets/42d9abfa-3f4a-44ba-b6b4-6700ab06832d"
/>

crates/ty_python_semantic/resources/mdtest/function/return_type.md

@@ -80,7 +80,7 @@ class Foo(Protocol):
     def f[T](self, v: T) -> T: ...
 
 t = (Protocol, int)
-reveal_type(t[0])  # revealed: <special form 'typing.Protocol'>
+reveal_type(t[0])  # revealed: <special-form 'typing.Protocol'>
 
 class Lorem(t[0]):
     def f(self) -> int: ...