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](caolan/async@v2.6.3...v2.6.4)

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

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

frontend/yarn.lock

@@ -1712,9 +1712,9 @@ async-validator@^3.0.3:
   integrity sha1-s4ty+cCMHShUjfE7smC2kIRIykk=
 
 async@^2.6.2:
-  version "2.6.3"
-  resolved "https://registry.npm.taobao.org/async/download/async-2.6.3.tgz?cache=0&other_urls=https%3A%2F%2Fregistry.npm.taobao.org%2Fasync%2Fdownload%2Fasync-2.6.3.tgz#d72625e2344a3656e3a3ad4fa749fa83299d82ff"
-  integrity sha1-1yYl4jRKNlbjo61Pp0n6gymdgv8=
+  version "2.6.4"
+  resolved "https://registry.yarnpkg.com/async/-/async-2.6.4.tgz#706b7ff6084664cd7eae713f6f965433b5504221"
+  integrity sha512-mzo5dfJYwAn29PeiJ0zvwTo04zj8HDJj0Mn8TD7sno7q12prdbnasKJHhkm2c1LgrhlJ0teaea8860oxi51mGA==
   dependencies:
     lodash "^4.17.14"
 
@@ -5411,9 +5411,9 @@ lodash.uniq@^4.5.0:
   integrity sha1-0CJTc662Uq3BvILklFM5qEJ1R3M=
 
 lodash@^4.17.11, lodash@^4.17.12, lodash@^4.17.13, lodash@^4.17.14, lodash@^4.17.15, lodash@^4.17.3, lodash@^4.17.5:
-  version "4.17.15"
-  resolved "https://registry.npm.taobao.org/lodash/download/lodash-4.17.15.tgz?cache=0&sync_timestamp=1563508077056&other_urls=https%3A%2F%2Fregistry.npm.taobao.org%2Flodash%2Fdownload%2Flodash-4.17.15.tgz#b447f6670a0455bbfeedd11392eff330ea097548"
-  integrity sha1-tEf2ZwoEVbv+7dETku/zMOoJdUg=
+  version "4.17.21"
+  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.21.tgz#679591c564c3bffaae8454cf0b3df370c3d6911c"
+  integrity sha512-v2kDEe57lecTulaDIuNTPy3Ry4gLGJ6Z1O3vE1krgXZNrsQ+LFTGHVxVjcXPs17LhbZVGedAJv8XZ1tvj5FvSg==
 
 log-symbols@^2.2.0:
   version "2.2.0"