Bump async from 3.2.1 to 3.2.4 in /backend

Bumps [async](https://github.com/caolan/async) from 3.2.1 to 3.2.4.
- [Release notes](https://github.com/caolan/async/releases)
- [Changelog](https://github.com/caolan/async/blob/master/CHANGELOG.md)
- [Commits](https://github.com/caolan/async/compare/v3.2.1...v3.2.4)

---
updated-dependencies:
- dependency-name: async
  dependency-type: indirect
...

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

backend/yarn.lock

@@ -246,9 +246,9 @@ astral-regex@^1.0.0:
   integrity sha512-+Ryf6g3BKoRc7jfp7ad8tM4TtMiaWvbF/1/sQcZPkkS7ag3D5nMBCe2UfOTONtAkaG0tO0ij3C5Lwmf1EiyjHg==
 
 async@^3.2.0:
-  version "3.2.1"
-  resolved "https://registry.yarnpkg.com/async/-/async-3.2.1.tgz#d3274ec66d107a47476a4c49136aacdb00665fc8"
-  integrity sha512-XdD5lRO/87udXCMC9meWdYiR+Nq6ZjUfXidViUZGu2F1MO4T3XwZ1et0hb2++BgLfhyJwy44BGB/yx80ABx8hg==
+  version "3.2.4"
+  resolved "https://registry.yarnpkg.com/async/-/async-3.2.4.tgz#2d22e00f8cddeb5fde5dd33522b56d1cf569a81c"
+  integrity sha512-iAB+JbDEGXhyIUavoDl9WP/Jj106Kz9DEn1DPgYw5ruDn0e3Wgi3sKFm55sASdGBNOQB8F59d9qQ7deqrHA8wQ==
 
 atob@^2.1.2:
   version "2.1.2"