[red-knot] Add a new Type::ProtocolInstance variant (take 2!)

crates/red_knot_python_semantic/resources/mdtest/import/builtins.md

@@ -7,15 +7,15 @@ Builtin symbols can be explicitly imported:
 ```py
 import builtins
 
-reveal_type(builtins.chr)  # revealed: def chr(i: int | SupportsIndex, /) -> str
+reveal_type(builtins.chr)  # revealed: def chr(i: SupportsIndex, /) -> str
 ```
 
 ## Implicit use of builtin
 
 Or used implicitly:
 
 ```py
-reveal_type(chr)  # revealed: def chr(i: int | SupportsIndex, /) -> str
+reveal_type(chr)  # revealed: def chr(i: SupportsIndex, /) -> str
 reveal_type(str)  # revealed: Literal[str]
 ```