Update rack and rouge gems to match GitLab Rails

This matches the versions used in GitLab Rails and helps reduce some
space in the Omnibus build.

Changelog: changed

ruby/Gemfile.lock

@@ -138,7 +138,7 @@ GEM
       method_source (~> 0.9.0)
     public_suffix (4.0.6)
     racc (1.6.0)
-    rack (2.2.3)
+    rack (2.2.4)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
     rails-dom-testing (2.0.3)
@@ -157,7 +157,7 @@ GEM
     reverse_markdown (1.4.0)
       nokogiri
     rexml (3.2.5)
-    rouge (3.27.0)
+    rouge (3.30.0)
     rspec (3.8.0)
       rspec-core (~> 3.8.0)
       rspec-expectations (~> 3.8.0)