Bump lodash from 4.17.14 to 4.17.21 in /functions

Bumps [lodash](https://github.com/lodash/lodash) from 4.17.14 to 4.17.21.
- [Release notes](https://github.com/lodash/lodash/releases)
- [Commits](https://github.com/lodash/lodash/compare/4.17.14...4.17.21)

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

functions/package-lock.json

@@ -2188,9 +2188,9 @@
       }
     },
     "lodash": {
-      "version": "4.17.14",
-      "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.17.14.tgz",
-      "integrity": "sha512-mmKYbW3GLuJeX+iGP+Y7Gp1AiGHGbXHCOh/jZmrawMmsE7MS4znI3RL2FsjbqOyMayHInjOeykW7PEajUk1/xw=="
+      "version": "4.17.21",
+      "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.17.21.tgz",
+      "integrity": "sha512-v2kDEe57lecTulaDIuNTPy3Ry4gLGJ6Z1O3vE1krgXZNrsQ+LFTGHVxVjcXPs17LhbZVGedAJv8XZ1tvj5FvSg=="
     },
     "lodash.at": {
       "version": "4.6.0",