fix: table of content is not scrollable

[ghost]

Closes #23542

What I did

Problem:
Table of content was not scrollable on overflowing.

Solution Result:

result.mp4

How to test

1. Enable TOC
2. Open component docs (ideally with many stories)
3. Make the viewport smaller so that TOC overflows

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)

Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli/src/sandbox-templates.ts
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "build", "documentation", "maintenance", "dependencies", "other"]

🦋 Canary release

This PR does not have a canary release associated. You can request a canary release of this pull request by mentioning the @storybookjs/core team here.

core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=<PR_NUMBER>

[vanessayuenn]

@cdedreuille can you take a look at this also? 🙏

[ndelangen]

Hello @vineetpradhanvp Thank you so much for contributing! It's really appreciated.

It seems like you might have missed that on the issue, @almoghaimo had also stated they were working on a fix.
Though your PR came in first it was @almoghaimo I'll be moving ahead with the PR from @almoghaimo.