Need to update font's color for the Add Feedback when device is in Dark Mode

[hffvld]

Description:

We need to update the font's color for the Add Feedback when the device is in Dark Mode.

Steps to Reproduce

1. Switch the device theme to the Dark Mode
2. Launch Brave > Open Leo
3. Send a query and wait for the answer
4. Tap and hold on the response
5. Dislike Answer > Observe

Actual result:

Hard to read Add Feedback when the device is in Dark Mode.

1	2

Expected result:

It must be easy to read Add Feedback when the device is in Dark Mode.

Reproduces how often: [Easily reproduced, Intermittent Issue]

Easily reproduced

Brave Version:

Brave build: 1.63 (177)
BraveCore: 1.63.177 (122.0.6261.128)

• Can you reproduce this issue with the most recent build from TestFlight? YES
• Can you reproduce this issue with the previous version of the current build from TestFlight? YES
• Can you reproduce this issue with the current build from AppStore? N/A

Device details:

iPhone 14 / iOS 17.4

Website problems only:

• Does the issue resolve itself when disabling Brave Shields?
• Is the issue reproducible on the latest version of Mobile Safari?

Additional Information

[kjozwiak]

The above requires 1.63.178 or higher for 1.63.x verification 👍

[kjozwiak]

Verification PASSED on iPhone 11 running iOS 17.4 using the following build(s):

1.63.178 Chromium: 122.0.6261.128 (Official Build) unknown (64-bit) 
--- | ---
Revision | 83e0e6978dea...
OS | iOS

Using the STR/Cases outlined via #36857 (comment), ensured that Add Feedback was visible for Dislike via both Light & Dark themes as per the following:

Liked

Example	Example

Disliked

Example	Example