Bump redcarpet from 3.4.0 to 3.5.1 in /website

Bumps [redcarpet](https://github.com/vmg/redcarpet) from 3.4.0 to 3.5.1.
- [Release notes](https://github.com/vmg/redcarpet/releases)
- [Changelog](https://github.com/vmg/redcarpet/blob/master/CHANGELOG.md)
- [Commits](vmg/redcarpet@v3.4.0...v3.5.1)

---
updated-dependencies:
- dependency-name: redcarpet
  dependency-type: indirect
...

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

website/Gemfile.lock

@@ -120,7 +120,7 @@ GEM
     rb-fsevent (0.9.8)
     rb-inotify (0.9.10)
       ffi (>= 0.5.0, < 2)
-    redcarpet (3.4.0)
+    redcarpet (3.5.1)
     rouge (2.1.1)
     sass (3.4.24)
     sprockets (2.12.4)