build(deps): bump leptos_actix from 0.5.6 to 0.6.4

Bumps [leptos_actix](https://github.com/leptos-rs/leptos) from 0.5.6 to 0.6.4.
- [Release notes](https://github.com/leptos-rs/leptos/releases)
- [Commits](leptos-rs/leptos@v0.5.6...v0.6.4)

---
updated-dependencies:
- dependency-name: leptos_actix
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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