Can't differentiate read and unread text in left panel

[iamjameswalters]

Describe the bug The left-hand panel text becomes white in dark mode, making it hard to spot the difference between read and unread messages.

To Reproduce Steps to reproduce the behavior:

1. Have an unread message.
2. Click on the Dark Mode toggle to enable Dark Mode

Expected behavior Historically, this styling on the left panel hasn't changed in dark mode, because this panel is already dark, and we don't modify its color any further in dark mode.

Screenshots Normal:

Dark Mode:

Desktop (please complete the following information):

• OS: Windows 10
• Browser: Firefox 84.0.2
• Rocket.Chat Server Version: 3.9.3