Website: upgrade lodash

Website tests use jsdom, and jsdom transitively depends on lodash.
lodash has a security advisory [1]. Let's upgrade lodash to fix the
potential security issue.

This commit should not change behavior.

[1] https://www.npmjs.com/advisories/1673

Author: strager

website/yarn.lock

@@ -705,9 +705,9 @@ lodash.sortby@^4.7.0:
   integrity sha1-7dFMgk4sycHgsKG0K7UhBRakJDg=
 
 lodash@^4.17.19:
-  version "4.17.20"
-  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.20.tgz#b44a9b6297bcb698f1c51a3545a2b3b368d59c52"
-  integrity sha512-PlhdFcillOINfeV7Ni6oF1TAEayyZBoZ8bcshTHqOYJYlrqzRK5hagpagky5o4HfCzzd1TRkXPMFq6cKk9rGmA==
+  version "4.17.21"
+  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.21.tgz#679591c564c3bffaae8454cf0b3df370c3d6911c"
+  integrity sha512-v2kDEe57lecTulaDIuNTPy3Ry4gLGJ6Z1O3vE1krgXZNrsQ+LFTGHVxVjcXPs17LhbZVGedAJv8XZ1tvj5FvSg==
 
 [email protected]:
   version "0.3.0"