spec/features/markdown/markdown_spec.rb is slow

Baseline:

gitlab-ce master % be rspec --profile -f Fuubar  --order defined spec/features/markdown/markdown_spec.rb

Top 10 slowest examples (48.66 seconds, 19.0% of total time):
  GitLab Markdown wiki pipeline behaves like all pipelines SanitizationFilter permits kbd elements
    5.1 seconds ./spec/features/markdown/markdown_spec.rb:100
  GitLab Markdown wiki pipeline behaves like all pipelines SanitizationFilter permits img elements
    5.1 seconds ./spec/features/markdown/markdown_spec.rb:108
  GitLab Markdown wiki pipeline includes RelativeLinkFilter
    5.02 seconds ./spec/features/markdown/markdown_spec.rb:283
  GitLab Markdown wiki pipeline behaves like all pipelines SanitizationFilter permits span elements
    4.82 seconds ./spec/features/markdown/markdown_spec.rb:120
  GitLab Markdown wiki pipeline behaves like all pipelines SanitizationFilter permits summary elements
    4.81 seconds ./spec/features/markdown/markdown_spec.rb:128
  GitLab Markdown wiki pipeline includes TableOfContentsFilter
    4.81 seconds ./spec/features/markdown/markdown_spec.rb:291
  GitLab Markdown wiki pipeline includes ColorFilter
    4.76 seconds ./spec/features/markdown/markdown_spec.rb:328
  GitLab Markdown wiki pipeline behaves like all pipelines SanitizationFilter permits br elements
    4.76 seconds ./spec/features/markdown/markdown_spec.rb:112
  GitLab Markdown wiki pipeline includes TaskListFilter
    4.75 seconds ./spec/features/markdown/markdown_spec.rb:312
  GitLab Markdown wiki pipeline behaves like all pipelines SanitizationFilter permits strike elements
    4.74 seconds ./spec/features/markdown/markdown_spec.rb:104

Finished in 4 minutes 15.6 seconds (files took 17.42 seconds to load)
75 examples, 0 failures