This function unregisters a rich text format that was previously registered using gtk_text_buffer_register_deserialize_format() or gtk_text_buffer_register_deserialize_tagset().
a #GdkAtom representing a registered rich text format.
2.10
See Implementation
This function unregisters a rich text format that was previously registered using gtk_text_buffer_register_deserialize_format() or gtk_text_buffer_register_deserialize_tagset().