Install Asciidoctor via Ruby Gem

Signed-off-by: Thomas Lauf <thomas.lauf@tngtech.com>

Author: lauft

test/docker/opensuse-tumbleweed

@@ -8,7 +8,9 @@ RUN zypper install -y \
            python3 \
            python3-python-dateutil \
            ruby \
-           ruby3.4-rubygem-asciidoctor
+           ruby-devel
+
+RUN gem install asciidoctor
 
 RUN update-alternatives --install /usr/bin/python python /usr/bin/python3 10
 ENV TZ=Europe/Berlin