build(deps-dev): bump @storybook/theming from 7.6.21 to 8.6.17

Bumps [@storybook/theming](https://github.com/storybookjs/storybook/tree/HEAD/code/lib/theming) from 7.6.21 to 8.6.17.
- [Release notes](https://github.com/storybookjs/storybook/releases)
- [Commits](https://github.com/storybookjs/storybook/commits/v8.6.17/code/lib/theming)

---
updated-dependencies:
- dependency-name: "@storybook/theming"
  dependency-version: 8.6.17
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

packages/storybook-angular/package.json

@@ -42,7 +42,7 @@
     "@storybook/manager-api": "8.6.15",
     "@storybook/mdx2-csf": "1.1.0",
     "@storybook/preset-scss": "1.0.3",
-    "@storybook/theming": "8.6.15",
+    "@storybook/theming": "8.6.17",
     "@types/node": "24.10.4",
     "@types/react": "18.3.27",
     "@utrecht/button-css": "workspace:*",

packages/storybook-helpers/package.json

@@ -19,7 +19,7 @@
     "lint-build": "tsc --noEmit --project tsconfig.json"
   },
   "devDependencies": {
-    "@storybook/theming": "7.6.21",
+    "@storybook/theming": "8.6.17",
     "remark": "15.0.1",
     "remark-normalize-headings": "4.0.0",
     "typescript": "5.9.3"