Bump redcarpet from 3.4.0 to 3.5.1

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)

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

Author: dependabot[bot]

Gemfile.lock

@@ -33,7 +33,7 @@ GEM
     rb-fsevent (0.10.2)
     rb-inotify (0.9.10)
       ffi (>= 0.5.0, < 2)
-    redcarpet (3.4.0)
+    redcarpet (3.5.1)
     rouge (2.2.1)
     safe_yaml (1.0.4)
     sass (3.5.2)