doc: Fix typo in generated section header
doc: Fix typo in generated section header

We were generating headers such as 'Events provided by wl_display events',
drop the last 'events'.

mchalupa/wayland,sir-murray/wayland,tulcod/wayland,mchalupa/wayland,bitfactor/wayland,abooij/wayland,tulcod/wayland,mchalupa/wayland,abooij/wayland,tulcod/wayland,eyolfson/wayland,bitfactor/wayland,eyolfson/wayland,sir-murray/wayland,abooij/wayland,eyolfson/wayland,bitfactor/wayland,sir-murray/wayland