MR widget buttons are inconsistent sizes

This issue is part of https://gitlab.com/gitlab-org/gitlab-ce/issues/33095

increase left/right padding of inline mr widget buttons 26px height as per original design

values:

font-size: 14px
line-height: 1
padding: 5px 8px
border-width: 1px

Design/Proposal

cc: @victorwu (making the https://gitlab.com/gitlab-org/gitlab-ce/issues/33095 more readable)