chore (npm): bump @storybook/theming from 8.6.7 to 8.6.12

Bumps [@storybook/theming](https://github.com/storybookjs/storybook/tree/HEAD/code/lib/theming) from 8.6.7 to 8.6.12.
- [Release notes](https://github.com/storybookjs/storybook/releases)
- [Commits](https://github.com/storybookjs/storybook/commits/v8.6.12/code/lib/theming)

---
updated-dependencies:
- dependency-name: "@storybook/theming"
  dependency-version: 8.6.12
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]