Github notifications pull request link typo (`pulls` -> `pull`)

### Routes ```routes /github/notifications ``` ### Full routes ```fullroutes /github/notifications ``` ### Related documentation https://docs.rsshub.app/routes/github#github-notifications ### What is expected? Links to notifications related to pull requests should lead to PRs. They look like this: github.com/matrix-org/matrix-spec-proposals/**_pull_**/2881 ### What is actually happening? Links lead to PR search page with query by author <number of the pr> because of the trailing "s". github.com/matrix-org/matrix-spec-proposals/**_pulls_**/2881 ### Deployment information Self-hosted ### Deployment information (for self-hosted) OS: Linux, Podman: 5.8.2, RSSHub ImageDigest: "sha256:fc8a4be2c4014d0dad9d28f5ae8cff9cbfddb3595f15fe9c2369d2e95a74fdf2" ### Additional info ```shell N/A ``` ### This is not a duplicated issue - [x] I have searched [existing issues](https://github.com/DIYgod/RSSHub/issues) to ensure this bug has not already been reported