gnu: awesome: Fix manual pages generation.

Since version 4.3, Awesome uses asciidoctor instead of asciidoc to
generate manual pages.
Reference: https://github.com/awesomeWM/awesome/commit/d9cc56538f05

* gnu/packages/wm.scm (awesome)[native-inputs]: Replace asciidoc with
ruby-asciidoctor.

Merges guix/guix!6833

Change-Id: Iacd2bba93889eb283d0cc771a8abb46b178c219c
Signed-off-by: Cayetano Santos <csantosb@inventati.org>

gnu/packages/wm.scm

@@ -1952,13 +1952,13 @@ for wlroots-based Wayland compositors.")
                         "awesome-4.3-fno-common.patch"))))
     (build-system cmake-build-system)
     (native-inputs
-     (list asciidoc
-           docbook-xsl
+     (list docbook-xsl
            doxygen
            gperf
            imagemagick
            lua-ldoc
            pkg-config
+           ruby-asciidoctor
            xmlto))
     (inputs
      (list bash-minimal