web: fix `web-standalone` proxy-warning contrast issue
Created by: valerybugakov
Context
While using the combination of yarn test-integration:debug and sg start web-standalone, tests will fail when they include a11y verification because the banner says that requests are proxied to another domain doesn't meet color contrast requirements.
This PR temporarily changes the text of the link inside of the banner. I created an issue to address the root cause of the problem later because the design input is needed.
Test plan
Ensure that the web-standalone warning doesn't cause the accessibility check error.
App preview:
Check out the client app preview documentation to learn more.