The command text 'Delete Duplicated Frames' used in the GPENCIL_MT_cleanup menu is not correct grammar for what the command does. Keyframes removed by this command may be duplicate keys without having been duplicated. It also does not match the name of the command in DOPESHEET_MT_context_menu.
space_dopesheet.py
This patch fixes the grammar, gets the command's text to match the DOPESHEET_MT_context_menu, and corrects the description in the Python API documentation.