Update rdoc requirement from = 6.3.0 to = 6.3.1

Updates the requirements on [rdoc](https://github.com/ruby/rdoc) to permit the latest version.
- [Release notes](https://github.com/ruby/rdoc/releases)
- [Changelog](https://github.com/ruby/rdoc/blob/master/History.rdoc)
- [Commits](https://github.com/ruby/rdoc/commits)

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

lazylead.gemspec

@@ -89,7 +89,7 @@ tasks instead of solving technical problems."
   s.add_development_dependency "net-ping", "2.0.8"
   s.add_development_dependency "rake", "13.0.3"
   s.add_development_dependency "random-port", "0.5.1"
-  s.add_development_dependency "rdoc", "6.3.0"
+  s.add_development_dependency "rdoc", "6.3.1"
   s.add_development_dependency "rubocop", "1.13.0"
   s.add_development_dependency "rubocop-minitest", "0.12.1"
   s.add_development_dependency "rubocop-performance", "1.11.1"