Bump rdoc from 6.15.1 to 6.16.0

Bumps [rdoc](https://github.com/ruby/rdoc) from 6.15.1 to 6.16.0.
- [Release notes](https://github.com/ruby/rdoc/releases)
- [Changelog](https://github.com/ruby/rdoc/blob/master/History.rdoc)
- [Commits](https://github.com/ruby/rdoc/compare/v6.15.1...v6.16.0)

---
updated-dependencies:
- dependency-name: rdoc
  dependency-version: 6.16.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Gemfile.lock

@@ -62,7 +62,7 @@ GEM
     em-websocket (0.5.3)
       eventmachine (>= 0.12.9)
       http_parser.rb (~> 0)
-    erb (5.1.3)
+    erb (6.0.0)
     erubis (2.7.0)
     espeak-ruby (1.1.0)
     event_emitter (0.2.6)
@@ -166,7 +166,7 @@ GEM
       rack (>= 1.3)
     rainbow (3.1.1)
     rake (13.3.1)
-    rdoc (6.15.1)
+    rdoc (6.16.0)
       erb
       psych (>= 4.0.0)
       tsort
@@ -237,7 +237,7 @@ GEM
     sqlite3 (2.8.0-x86_64-darwin)
     sqlite3 (2.8.0-x86_64-linux-gnu)
     sqlite3 (2.8.0-x86_64-linux-musl)
-    stringio (3.1.7)
+    stringio (3.1.8)
     sync (0.5.0)
     term-ansicolor (1.11.3)
       tins (~> 1)
@@ -325,7 +325,7 @@ DEPENDENCIES
   rack (~> 3.2)
   rack-protection (~> 4.2.1)
   rake (~> 13.3)
-  rdoc (~> 6.15)
+  rdoc (~> 6.16)
   rest-client (~> 2.1.0)
   rspec (~> 3.13)
   rubocop (~> 1.81.7)