Bump rdoc from 6.0.1 to 6.0.2 (#30)

Bumps [rdoc](https://github.com/ruby/rdoc) from 6.0.1 to 6.0.2.
- [Release notes](https://github.com/ruby/rdoc/releases)
- [Changelog](https://github.com/ruby/rdoc/blob/master/History.rdoc)
- [Commits](ruby/rdoc@v6.0.1...v6.0.2)

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

Gemfile.lock

@@ -67,7 +67,7 @@ GEM
     multi_json (1.13.1)
     multi_test (0.1.2)
     rake (12.3.0)
-    rdoc (6.0.1)
+    rdoc (6.0.2)
     rspec (3.7.0)
       rspec-core (~> 3.7.0)
       rspec-expectations (~> 3.7.0)