Update docs submodule to fix troff-less builds
Update docs submodule to fix troff-less builds

Pull in changes from https://github.com/dita-ot/docs/pull/274 after troff
plug-in was unbundled for https://github.com/dita-ot/dita-ot/pull/3364

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

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