ad used, when "as" was probably better

[gunnarahlberg]

The following sentence says "Each shorthand takes the same arguments ad Find, except for the ~horiz and ~vert arguments."

https://github.com/racket/rhombus-prototype/blob/9e934a7ac967c2c4b8ea8616d208458006aba9b4/rhombus/pict/scribblings/find.scrbl#L121

Yet, the word "ad" should probably be replaced by "as"

[mflatt]

Fixed by #507