Few more fixes for issues found by testing on internal codebases (#4876)

Few unrelated (but quite obvious) fixes here.

Co-authored-by: Ivan Levkivskyi <ilevkivskyi@dropbox.com>

third_party/2and3/markdown/postprocessors.pyi

@@ -5,7 +5,7 @@ from . import util
 def build_postprocessors(md, **kwargs): ...
 
 class Postprocessor(util.Processor):
-    def run(self, text) -> None: ...
+    def run(self, text) -> Any: ...
 
 class RawHtmlPostprocessor(Postprocessor):
     def isblocklevel(self, html): ...

third_party/2and3/markdown/treeprocessors.pyi

@@ -6,7 +6,7 @@ def build_treeprocessors(md, **kwargs): ...
 def isString(s): ...
 
 class Treeprocessor(util.Processor):
-    def run(self, root) -> None: ...
+    def run(self, root) -> Optional[Any]: ...
 
 class InlineProcessor(Treeprocessor):
     inlinePatterns: Any