build(deps): bump async from 2.6.3 to 2.6.4 in /frontend

Bumps [async](https://github.com/caolan/async) from 2.6.3 to 2.6.4.
- [Release notes](https://github.com/caolan/async/releases)
- [Changelog](https://github.com/caolan/async/blob/v2.6.4/CHANGELOG.md)
- [Commits](https://github.com/caolan/async/compare/v2.6.3...v2.6.4)

---
updated-dependencies:
- dependency-name: async
  dependency-type: indirect
...
Signed-off-by: Ndependabot[bot] <support@github.com>

frontend/yarn.lock

@@ -3966,9 +3966,9 @@ async-validator@^4.1.0:
   integrity sha512-7HhHjtERjqlNbZtqNqy2rckN/SpOOlmDliet+lP7k+eKZEjPk3DgyeU9lIXLdeLz0uBbbVp+9Qdow9wJWgwwfg==
 
 async@^2.6.1, async@^2.6.2, async@^2.6.3, async@~2.6.1:
-  version "2.6.3"
-  resolved "https://registry.yarnpkg.com/async/-/async-2.6.3.tgz#d72625e2344a3656e3a3ad4fa749fa83299d82ff"
-  integrity sha512-zflvls11DCy+dQWzTW2dzuilv8Z5X/pjfmZOWba6TNIVDm+2UDaJmXSOXlasHKfNBs8oo3M0aT50fDEWfKZjXg==
+  version "2.6.4"
+  resolved "https://registry.yarnpkg.com/async/-/async-2.6.4.tgz#706b7ff6084664cd7eae713f6f965433b5504221"
+  integrity sha512-mzo5dfJYwAn29PeiJ0zvwTo04zj8HDJj0Mn8TD7sno7q12prdbnasKJHhkm2c1LgrhlJ0teaea8860oxi51mGA==
   dependencies:
     lodash "^4.17.14"