gnu: Use ghostscript over ghostscript-gs.

* gnu/packages/engineering.scm (fastcap)[native-inputs],
gnu/packages/lout.scm (lout)[native-inputs],
gnu/packages/ocaml.scm (unison)[native-inputs],
gnu/packages/plotutils.scm (asymptote)[native-inputs],
gnu/packages/skribilo.scm (skribilo)[native-inputs]: Remove
ghostscript-gs.
* gnu/packages/gv.scm (gv)[propagated-inputs],
gnu/packages/music.scm (lilypond)[inputs],
gnu/packages/scheme.scm (chez-scheme)[native-inputs]: Use
ghostscript over ghostscript-gs.

gnu/packages/lout.scm

@@ -88,8 +88,7 @@
     (build-system gnu-build-system)               ; actually, just a makefile
     (outputs '("out" "doc"))
     (native-inputs
-     `(("ghostscript" ,ghostscript)
-       ("ghostscript-gs" ,ghostscript-gs)))
+     `(("ghostscript" ,ghostscript)))
     (arguments `(#:modules ((guix build utils)
                             (guix build gnu-build-system)
                             (srfi srfi-1))        ; we need SRFI-1