Bump tauri-plugin-single-instance in /src-tauri

Bumps [tauri-plugin-single-instance](https://github.com/tauri-apps/plugins-workspace) from `b8bf4ad` to `3449dd5`.
- [Release notes](https://github.com/tauri-apps/plugins-workspace/releases)
- [Commits](tauri-apps/plugins-workspace@b8bf4ad...3449dd5)

---
updated-dependencies:
- dependency-name: tauri-plugin-single-instance
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>