Bump the test group with 1 update

Bumps the test group with 1 update: [@axe-core/puppeteer](https://github.com/dequelabs/axe-core-npm).

- [Release notes](https://github.com/dequelabs/axe-core-npm/releases)
- [Changelog](https://github.com/dequelabs/axe-core-npm/blob/develop/CHANGELOG.md)
- [Commits](https://github.com/dequelabs/axe-core-npm/commits)

---
updated-dependencies:
- dependency-name: "@axe-core/puppeteer"
  dependency-type: direct:development
  update-type: version-update:semver-minor
  dependency-group: test
...

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

shared/helpers/package.json

@@ -14,7 +14,7 @@
   },
   "license": "MIT",
   "devDependencies": {
-    "@axe-core/puppeteer": "^4.7.3",
+    "@axe-core/puppeteer": "^4.8.1",
     "@govuk-frontend/config": "*",
     "@govuk-frontend/lib": "*",
     "cheerio": "^1.0.0-rc.12",