+ cancel form :ooo{ss,jj,rr} -> :oo{s,j,r}

Normally the cancel form of :oooss -> :ooos, however we
have a trick of :ooos to support some French-based words,
and we would also want to cancel to accent + trick.

This is to type :moosefs successfully. Without this cancel

form, typing :moosefs requires a manual commit.

See also https://github.com/TheSLinux/gs/issues/26
(comment #issuecomment-21686091)