Removed recently broken "doc-tests.rkt"
Removed recently broken "doc-tests.rkt"

The breakage was from `declare-exporting' now requiring at least one
module path. Plot's docs build makes the test superfluous, anyway.

mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket