Update Ruby dependency: 2.5.8 → 2.5.9 (patch)

Targets:

    docker run --rm \
        registry.opensuse.org/opensuse/infrastructure/osem/containers/osem/base \
        ruby --version

See also:

  - openSUSE#2646
  - openSUSE#2680

Gemfile

@@ -2,7 +2,7 @@
 
 source 'https://rubygems.org'
 
-ruby ENV['OSEM_RUBY_VERSION'] || '2.5.8'
+ruby ENV['OSEM_RUBY_VERSION'] || '2.5.9'
 
 # rails-assets requires >= 1.8.4
 if Gem::Version.new(Bundler::VERSION) < Gem::Version.new('1.8.4')