Bump json in /pkg/mod/github.com/hashicorp/serf@v0.8.2/website

Bumps [json](https://github.com/flori/json) from 2.1.0 to 2.3.1.
- [Release notes](https://github.com/flori/json/releases)
- [Changelog](https://github.com/flori/json/blob/master/CHANGES.md)
- [Commits](https://github.com/flori/json/compare/v2.1.0...v2.3.1)
Signed-off-by: Ndependabot[bot] <support@github.com>

pkg/mod/github.com/hashicorp/serf@v0.8.2/website/Gemfile.lock

@@ -50,7 +50,7 @@ GEM
       uber (~> 0.0.14)
     http_parser.rb (0.6.0)
     i18n (0.7.0)
-    json (2.1.0)
+    json (2.3.1)
     kramdown (1.15.0)
     listen (3.0.8)
       rb-fsevent (~> 0.9, >= 0.9.4)