Add 'enum' to spelling private dict

Fix pylint wrong-spelling-in-comment (C0401) for the word 'enum' in
the VuMark exception comments.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Author: adamtheturtle

spelling_private_dict.txt

@@ -42,6 +42,7 @@ decodable
 dev
 dict
 docstring
+enum
 filename
 foo
 formdata