Fix color assigment of feedback list rows in dark mode

[MizukiTemma]

Describe the Bug

As a part of #515, the feedback list has no longer the alternating row colors (earlier uneven row had gray background). This change has been affecting the dark mode too and one cannot read the last three columns.

Steps to Reproduce

1. Change to the dark mode
2. Go to the feedback list
3. See entries in the columns "Content type", "Submitted on" and "Marked as read by" are invisible (because of the color combination) in uneven rows

Expected Behavior

Entries are visible

Actual Behavior

They are not 😿

Additional Information