Bump sockjs from 0.3.19 to 0.3.21 in /twistter-frontend

Bumps [sockjs](https://github.com/sockjs/sockjs-node) from 0.3.19 to 0.3.21.
- [Release notes](https://github.com/sockjs/sockjs-node/releases)
- [Changelog](https://github.com/sockjs/sockjs-node/blob/v0.3.21/Changelog)
- [Commits](https://github.com/sockjs/sockjs-node/compare/v0.3.19...v0.3.21)

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

functions/package-lock.json

@@ -673,14 +673,6 @@
         "readable-stream": "~1.0.32"
       }
     },
-    "busboy": {
-      "version": "0.3.1",
-      "resolved": "https://registry.npmjs.org/busboy/-/busboy-0.3.1.tgz",
-      "integrity": "sha512-y7tTxhGKXcyBxRKAni+awqx8uqaJKrSFSNFSeRG5CsWNdmy2BIK+6VGWEW7TZnIO/533mtMEA4rOevQV815YJw==",
-      "requires": {
-        "dicer": "0.3.0"
-      }
-    },
     "bytebuffer": {
       "version": "5.0.1",
       "resolved": "https://registry.npmjs.org/bytebuffer/-/bytebuffer-5.0.1.tgz",
@@ -2601,9 +2593,9 @@
       }
     },
     "lodash": {
-      "version": "4.17.21",
-      "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.17.21.tgz",
-      "integrity": "sha512-v2kDEe57lecTulaDIuNTPy3Ry4gLGJ6Z1O3vE1krgXZNrsQ+LFTGHVxVjcXPs17LhbZVGedAJv8XZ1tvj5FvSg=="
+      "version": "4.17.15",
+      "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.17.15.tgz",
+      "integrity": "sha512-8xOcRHvCjnocdS5cpwXQXVzmmh5e5+saE2QGoeQmbKmRS6J3VQppPOIt0MnmE+4xlZoumy0GPG0D0MVIQbNA1A=="
     },
     "lodash.at": {
       "version": "4.6.0",