brave://discards table header is unreadable on dark theme

[LaurenWags]

Description

Found while testing #10451

The table header on brave://discards page is unreadable on dark theme. Looks fine on light theme.

Does not reproduce on Chrome.

Steps to Reproduce

1. Have dark theme set
2. Navigate to brave://discards
3. Table header is unreadable (white text on light blue background)
4. Switch to light theme
5. Table header is readable

Actual result:

Dark	Light

Expected result:

Chrome's dark themed page for comparison

Reproduces how often:

easily

Brave version (brave://version info)

Brave	1.19.84 Chromium: 88.0.4324.87 (Official Build) (x86_64)
Revision	dd01ff8f58c65af81127ad5c105c79d5b571d8f3-refs/branch-heads/4324@{#1702}
OS	macOS Version 10.15.7 (Build 19H15)

Version/Channel Information:

• Can you reproduce this issue with the current release? 1.18.x is n/a (broken), 1.19.x yes
• Can you reproduce this issue with the beta channel? 1.20.x yes
• Can you reproduce this issue with the nightly channel? 1.21.x yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? n/a
• Does the issue resolve itself when disabling Brave Rewards? n/a
• Is the issue reproducible on the latest version of Chrome? no

Miscellaneous Information:

cc @rebron @brave/legacy_qa

[wyatt400]

@rebron Seems fixed, test this again, should close this issue.