chore(deps-dev): bump @vuepress/plugin-back-to-top

Bumps [@vuepress/plugin-back-to-top](https://github.com/vuejs/vuepress/tree/HEAD/packages/@vuepress/plugin-back-to-top) from 2.0.0-beta.68 to 2.0.0-rc.0.
- [Release notes](https://github.com/vuejs/vuepress/releases)
- [Changelog](https://github.com/vuejs/vuepress/blob/master/CHANGELOG.md)
- [Commits](https://github.com/vuejs/vuepress/commits/HEAD/packages/@vuepress/plugin-back-to-top)

---
updated-dependencies:
- dependency-name: "@vuepress/plugin-back-to-top"
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

package.json

@@ -46,7 +46,7 @@
     "userscript"
   ],
   "devDependencies": {
-    "@vuepress/plugin-back-to-top": "^2.0.0-beta.68",
+    "@vuepress/plugin-back-to-top": "^2.0.0-rc.0",
     "@vuepress/plugin-google-analytics": "^2.0.0-beta.68",
     "typescript": "5.2.2",
     "vuepress": "^2.0.0-beta.68"