Deprecate legacy `gen-user-*` templates
Deprecate legacy `gen-user-*` templates

Per https://github.com/dita-ot/dita-ot/pull/3770#issuecomment-939352049

Signed-off-by: Roger Sheen <a61a1add71dadc74037ae5e44ee30713db9a7451@infotexture.net>

shaneataylor/dita-ot,shaneataylor/dita-ot,infotexture/dita-ot,shaneataylor/dita-ot,dita-ot/dita-ot,infotexture/dita-ot,dita-ot/dita-ot,infotexture/dita-ot,dita-ot/dita-ot,shaneataylor/dita-ot,shaneataylor/dita-ot,dita-ot/dita-ot,infotexture/dita-ot,dita-ot/dita-ot,infotexture/dita-ot