build(deps): bump @vue/cli-plugin-unit-mocha in /website/client (#13607)

Bumps [@vue/cli-plugin-unit-mocha](https://github.com/vuejs/vue-cli/tree/HEAD/packages/@vue/cli-plugin-unit-mocha) from 4.5.14 to 4.5.15.
- [Release notes](https://github.com/vuejs/vue-cli/releases)
- [Changelog](https://github.com/vuejs/vue-cli/blob/dev/CHANGELOG.md)
- [Commits](https://github.com/vuejs/vue-cli/commits/v4.5.15/packages/@vue/cli-plugin-unit-mocha)

---
updated-dependencies:
- dependency-name: "@vue/cli-plugin-unit-mocha"
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

website/client/package.json

@@ -22,7 +22,7 @@
     "@vue/cli-plugin-babel": "^4.5.15",
     "@vue/cli-plugin-eslint": "^4.5.14",
     "@vue/cli-plugin-router": "^4.5.15",
-    "@vue/cli-plugin-unit-mocha": "^4.5.14",
+    "@vue/cli-plugin-unit-mocha": "^4.5.15",
     "@vue/cli-service": "^4.5.15",
     "@vue/test-utils": "1.0.0-beta.29",
     "amplitude-js": "^8.9.1",