bs4: Make Tag.attrs more permissive (#11487)

Make `Tag.attrs` more permissive to be in line with actual code

`Tag.attrs` is a dict can technically have `list[str]` as a valid value, not just `str`. Making the value type a union with `Any` allows `list[str]` to be valid in a type checker's eyes if a user narrows it.

Based on discussion in, and fixes, #8755.

stubs/beautifulsoup4/bs4/element.pyi

@@ -234,7 +234,7 @@ class Tag(PageElement):
     sourceline: int | None
     sourcepos: int | None
     known_xml: bool | None
-    attrs: dict[str, str]
+    attrs: dict[str, str | Any]
     contents: list[PageElement]
     hidden: bool
     can_be_empty_element: bool | None