fix: update appearance/index.ts to apply the accent color on tabs

[DenysMb]

Pre-flight Checklist

Please ensure you've completed all of the following.

• I have read the Contributing Guidelines for this project.
• I agree to follow the Code of Conduct that this project adheres to.

Description of Change

After this previous PR #1944, as stated by @wvds here #1944 (comment), the accent color was not being updated in tabs. This happened because, with the change from border to box-shadow, I forgot to update the appearance/index.ts, where we do this change. It was still changing the border-color, but since there is no more border, it was doing nothing. I just needed to update the code there to use the box-shadow.

Motivation and Context

This is a bug.

Screenshots

Checklist

• My pull request is properly named
• The changes respect the code style of the project (pnpm prepare-code)
• pnpm test passes
• I tested/previewed my changes locally

Release Notes

Fix the problem that was causing the accent colors to not be applied to tabs indicator

[vraravam]

@DenysMb - Thanks for creating the PR so quickly, but please create PRs using the latest commit from the develop branch. Otherwise, all testing (especially visual changes) will not be verifiable in the correct manner.
And, of course, the CI runs unnecessarily.

[DenysMb]

@vraravam Yeah, sorry. I forgot to fetch the changes before I made the changes.

[vraravam]

@vraravam Yeah, sorry. I forgot to fetch the changes before I made the changes.

Please retest with the latest version since I have rebased from the latest develop. Once you do and confirm that the fix works, we can merge (after the CI run also completes successfully)

[DenysMb]

@vraravam Everything working fine here after the rebase.

[vraravam]

not tested by myself. OP says its working.