docs: Fix typo in addon README

[Sidnioulz]

I did not open an issue for this because it is so trivial.

What I did

I removed an accidental backtick in a README file.

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

not applicable

Manual testing

1. Visit https://github.com/storybookjs/storybook/tree/next/code/addons/themes
2. Notice backtick in title

Documentation

not applicable

Checklist for 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:

  Available labels

  • bug: Internal changes that fixes incorrect behavior.
  • maintenance: User-facing maintenance tasks.
  • dependencies: Upgrading (sometimes downgrading) dependencies.
  • build: Internal-facing build tooling & test updates. Will not show up in release changelog.
  • cleanup: Minor cleanup style change. Will not show up in release changelog.
  • documentation: Documentation only changes. Will not show up in release changelog.
  • feature request: Introducing a new feature.
  • BREAKING CHANGE: Changes that break compatibility in some way with current major version.
  • other: Changes that don't fit in the above categories.

🦋 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>

[jonniebigodes]

@Sidnioulz thanks for taking the time to put together this pull request and catch that small but rather important typo in the documentation. Appreciate it 🙏 ! I've checked, and looks good to me. I'm going to go ahead and get this one in once the checklist clears.

Hope you have a great day.

Stay safe

cc @integrayshaun

[jonniebigodes]

Merging as the resulting failures are unrelated to this, and this is a documentation-only pr.