Bump rdoc from 6.4.0 to 6.4.1.1

Bumps [rdoc](https://github.com/ruby/rdoc) from 6.4.0 to 6.4.1.1.
- [Release notes](https://github.com/ruby/rdoc/releases)
- [Changelog](https://github.com/ruby/rdoc/blob/master/History.rdoc)
- [Commits](ruby/rdoc@v6.4.0...v6.4.1.1)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -57,15 +57,15 @@ GEM
       racc (~> 1.4)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
-    psych (4.0.6)
+    psych (5.1.2)
       stringio
     public_suffix (5.0.0)
     racc (1.7.3)
     rake (13.0.6)
     rb-fsevent (0.11.2)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
-    rdoc (6.4.0)
+    rdoc (6.4.1.1)
       psych (>= 4.0.0)
     rexml (3.2.5)
     rouge (3.30.0)
@@ -77,7 +77,7 @@ GEM
       rb-inotify (~> 0.9, >= 0.9.7)
     sassc (2.4.0)
       ffi (~> 1.9)
-    stringio (3.0.2)
+    stringio (3.1.0)
     temple (0.8.2)
     terminal-table (2.0.0)
       unicode-display_width (~> 1.1, >= 1.1.1)