Prune unneeded gitlab-glfm-markdown precompiled libraries

gitlab-glfm-markdown ships with precompiled shared libraries for all
supported Ruby versions. Just as we do with nokogiri and other gems,
keep only the version needed for the current Ruby version.

Changelog: changed

Author: stanhu

config/software/gitlab-rails.rb

@@ -128,6 +128,7 @@
 
     ruby_ver = shellout!("#{embedded_bin('ruby')} -e 'puts RUBY_VERSION.match(/\\d+\\.\\d+/)[0]'", env: env).stdout.chomp
     gem_paths = {
+      'gitlab-glfm-markdown' => 'lib',
       'google-protobuf' => 'lib/google',
       'grpc' => 'src/ruby/lib/grpc',
       'prometheus-client-mmap' => 'lib',