Upgrade yarn to 1.22.21 in WORKSPACE.bazel (#175632)

In addition to #175495

Author: jbudz

WORKSPACE.bazel

@@ -33,9 +33,9 @@ node_repositories(
     "https://us-central1-elastic-kibana-184716.cloudfunctions.net/kibana-ci-proxy-cache/dist/v{version}/{filename}",
   ],
   yarn_repositories = {
-    "1.22.19": ("yarn-v1.22.19.tar.gz", "yarn-v1.22.19", "732620bac8b1690d507274f025f3c6cfdc3627a84d9642e38a07452cc00e0f2e"),
+    "1.22.21": ("yarn-v1.22.21.tar.gz", "yarn-v1.22.21", "a55bb4e85405f5dfd6e7154a444e7e33ad305d7ca858bad8546e932a6688df08"),
   },
-  yarn_version = "1.22.19",
+  yarn_version = "1.22.21",
   yarn_urls = [
     "https://github.com/yarnpkg/yarn/releases/download/v{version}/{filename}",
   ],