Mark stub-only private symbols as @type_check_only in third-party stubs (#14545)

stubs/bleach/bleach/callbacks.pyi

@@ -1,11 +1,12 @@
 from collections.abc import MutableMapping
-from typing import Protocol
+from typing import Protocol, type_check_only
 from typing_extensions import TypeAlias
 
 from bleach import _HTMLAttrKey
 
 _HTMLAttrs: TypeAlias = MutableMapping[_HTMLAttrKey, str]
 
+@type_check_only
 class _Callback(Protocol):  # noqa: Y046
     def __call__(self, attrs: _HTMLAttrs, new: bool = ..., /) -> _HTMLAttrs: ...
 

stubs/bleach/bleach/html5lib_shim.pyi

@@ -1,7 +1,7 @@
 import re
 from codecs import CodecInfo
 from collections.abc import Generator, Iterable, Iterator
-from typing import Any, Final, Protocol
+from typing import Any, Final, Protocol, type_check_only
 
 # We don't re-export any `html5lib` types / values here, because they are not
 # really public and may change at any time. This is just a helper module,
@@ -14,6 +14,7 @@ from html5lib.serializer import HTMLSerializer
 from html5lib.treewalkers.base import TreeWalker
 
 # Is actually webencodings.Encoding
+@type_check_only
 class _Encoding(Protocol):
     name: str
     codec_info: CodecInfo