Remove type alias _CallableElement in ElementTree (#14476)

Remove _CallableElement and make _ElementCallable recursive

Author: srittau

stdlib/xml/etree/ElementTree.pyi

@@ -80,7 +80,6 @@ def canonicalize(
 # The tag for Element can be set to the Comment or ProcessingInstruction
 # functions defined in this module.
 _ElementCallable: TypeAlias = Callable[..., Element[_ElementCallable]]
-_CallableElement: TypeAlias = Element[_ElementCallable]
 
 _Tag = TypeVar("_Tag", default=str, bound=str | _ElementCallable)
 _OtherTag = TypeVar("_OtherTag", default=str, bound=str | _ElementCallable)
@@ -137,8 +136,8 @@ class Element(Generic[_Tag]):
     def __bool__(self) -> bool: ...
 
 def SubElement(parent: Element, tag: str, attrib: dict[str, str] = ..., **extra: str) -> Element: ...
-def Comment(text: str | None = None) -> _CallableElement: ...
-def ProcessingInstruction(target: str, text: str | None = None) -> _CallableElement: ...
+def Comment(text: str | None = None) -> Element[_ElementCallable]: ...
+def ProcessingInstruction(target: str, text: str | None = None) -> Element[_ElementCallable]: ...
 
 PI = ProcessingInstruction