[web] Introduce colors for relationship action buttons

Summary:
The buttons in the relationship chat settings now have colors that are consistent with the other relationship prompt buttons found in the app

Depends on D5088

Test Plan:
Please view the screenshots to see the before and after of the changes I made:

Before:
All buttons in the relationship chat settings modal looked like this:

After:
Update: The colors of the buttons are the same; however, there are no more icons

Add friend and block case

Withdraw friend request case

Accept and reject friend request case

unfriend case

unblock case

Reviewers: atul

Reviewed By: atul

Subscribers: ashoat, tomek, atul, abosh

Differential Revision: https://phab.comm.dev/D5100