Add BadRequest, InvalidAcceptHeader, InvalidInstanceId to spelling dict

Fix Sphinx spell checker failures for the result code names used in the
new exception docstrings.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: adamtheturtle

spelling_private_dict.txt

@@ -1,9 +1,12 @@
 AuthenticationFailure
 BadImage
+BadRequest
 ConnectionErrorPossiblyImageTooLarge
 DateRangeError
 ImageTooLarge
 InactiveProject
+InvalidAcceptHeader
+InvalidInstanceId
 JSONDecodeError
 MatchProcessing
 MaxNumResultsOutOfRange