Bump rdoc from 6.12.0 to 6.13.0

Bumps [rdoc](https://github.com/ruby/rdoc) from 6.12.0 to 6.13.0.
- [Release notes](https://github.com/ruby/rdoc/releases)
- [Changelog](https://github.com/ruby/rdoc/blob/master/History.rdoc)
- [Commits](ruby/rdoc@v6.12.0...v6.13.0)

---
updated-dependencies:
- dependency-name: rdoc
  dependency-type: indirect
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -299,7 +299,7 @@ GEM
     rb-fsevent (0.11.2)
     rb-inotify (0.11.1)
       ffi (~> 1.0)
-    rdoc (6.12.0)
+    rdoc (6.13.0)
       psych (>= 4.0.0)
     redcarpet (3.6.1)
     redis (5.4.0)