Separator (hr) elements in wiki page should be darker
Summary
When adding a separator in a markdown wiki page, saving and viewing the page, the separator is in very light gray and really hard to see.
Steps to reproduce
Edit a wiki page, and add a separator within the page (markdown syntax) :
some text
---
some other text
After saving, the page includes the separator, but it is very light and hard to see.
Expected behavior
It should be in a darker shade of gray.
Actual behavior
Too light shade of gray.
Relevant logs and/or screenshots
Output of checks
Happens on my installation at work (GitLab Community Edition 8.15.2 790035fc)
Possible fixes
I don't have the problem when editing a wiki page and accessing the Preview pane:
When checking the differences in CSS, I see an additional style applied to the preview pane, defined here:

