Bump rdoc from 6.3.2 to 6.3.4.1 (#50)

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:development
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile.lock

@@ -26,7 +26,7 @@ GEM
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
     rake (13.0.3)
-    rdoc (6.3.2)
+    rdoc (6.3.4.1)
     rest-client (2.1.0)
       http-accept (>= 1.7.0, < 2.0)
       http-cookie (>= 1.0.2, < 2.0)