Remove some old hover styles from date columns in the dashboard.
Review Request #10183 — Created Sept. 26, 2018 and submitted
The dashboard styles for date columns had some old hover state
background color changes which weren't removed when we removed most of
the other hover styles. This resulted in some background color changes,
but only on odd rows. This change gets rid of them entirely.
Looked at my dashboard and saw that there were no more background color
changes on hover for date columns.