Bump actix-web from 4.0.0-beta.19 to 4.0.0-beta.20

Bumps [actix-web](https://github.com/actix/actix-web) from 4.0.0-beta.19 to 4.0.0-beta.20.
- [Release notes](https://github.com/actix/actix-web/releases)
- [Changelog](https://github.com/actix/actix-web/blob/master/CHANGES.md)
- [Commits](https://github.com/actix/actix-web/compare/web-v4.0.0-beta.19...web-v4.0.0-beta.20

)

---
updated-dependencies:
- dependency-name: actix-web
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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