Remove trash kcm docbook from kio-extras

the trash kcm docbook  will be imported from kde-runtime master with history into frameworks/kio where the code is, see https://git.reviewboard.kde.org/r/128912/
this docbook was imported into kio-extras with https://cgit.kde.org/kio-extras.git/commit/doc/kcontrol/trash/index.docbook?id=09cd27cca7daa2339960efa0ab852ad492b5ac97 but why?
REVIEW:129377