Fix mini graph pipeline breaking in merge request view

What does this MR do?

Sets a specific width to the table cell in order to force the graph to break in a specific point.

After this width, if the graph does not break, when hovering the last stage, the dropdown won't fit causing it to break at that moment.

It is an hacky solution. Me and @annabeldunstone discussed it on slack and we could not find a better one.

Screenshots (if relevant)

Screen_Recording_2017-09-15_at_05.32_PM__1_

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Review
  • Has been reviewed by Frontend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #37590 (closed)