Bump rdoc from 6.2.1 to 6.3.1

Bumps [rdoc](https://github.com/ruby/rdoc) from 6.2.1 to 6.3.1.
- [Release notes](https://github.com/ruby/rdoc/releases)
- [Changelog](https://github.com/ruby/rdoc/blob/master/History.rdoc)
- [Commits](ruby/rdoc@v6.2.1...v6.3.1)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -10,7 +10,7 @@ GEM
     byebug (11.1.1)
     diff-lcs (1.3)
     rake (12.3.3)
-    rdoc (6.2.1)
+    rdoc (6.3.1)
     rspec (3.9.0)
       rspec-core (~> 3.9.0)
       rspec-expectations (~> 3.9.0)