Bump rdoc from 6.3.2 to 6.3.4.1

Bumps [rdoc](https://github.com/ruby/rdoc) from 6.3.2 to 6.3.4.1.
- [Release notes](https://github.com/ruby/rdoc/releases)
- [Changelog](https://github.com/ruby/rdoc/blob/master/History.rdoc)
- [Commits](ruby/rdoc@v6.3.2...v6.3.4.1)

---
updated-dependencies:
- dependency-name: rdoc
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -138,7 +138,7 @@ GEM
     rainbow (3.0.0)
     rake (13.0.1)
     rchardet (1.8.0)
-    rdoc (6.3.2)
+    rdoc (6.3.4.1)
     reek (5.6.0)
       codeclimate-engine-rb (~> 0.4.0)
       kwalify (~> 0.7.0)