Merge pull request #1252 from alphagov/dependabot/bundler/rdoc-6.6.3.1

Bump rdoc from 6.6.2 to 6.6.3.1

Author: callumknights

Gemfile.lock

@@ -547,7 +547,7 @@ GEM
     rb-fsevent (0.11.2)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
-    rdoc (6.6.2)
+    rdoc (6.6.3.1)
       psych (>= 4.0.0)
     regexp_parser (2.9.0)
     reline (0.4.3)