Make push events have equal vertical spacing.

What does this MR do?

Evens out the vertical space between lines in push events.

Are there points in the code the reviewer needs to double check?

Not afaik.

Why was this MR needed?

UI consistency.

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/19517

Screenshots (if relevant)

Before: After:

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together

cc: @winniehell