Repository Page - Reduce cognitive load by right-aligning the Last Update column

By right aligning the Last Update column, we ensure that the item with heaviest weight (days, hours, months, years) is aligned - making it easier for the user to visually scan the data.

Original:

Screen_Shot_2016-07-07_at_1.42.17_PM

Proposed:

Screen_Shot_2016-07-07_at_1.43.21_PM

Central Issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/19610