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](ruby/rdoc@v6.15.1...v6.16.0)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -134,7 +134,7 @@ GEM
       thor (>= 0.19, < 2)
     diff-lcs (1.6.2)
     drb (2.2.3)
-    erb (5.1.3)
+    erb (6.0.0)
     erubi (1.13.1)
     et-orbi (1.4.0)
       tzinfo
@@ -303,7 +303,7 @@ GEM
     rainbow (3.1.1)
     rake (13.3.1)
     rdiscount (2.2.7.3)
-    rdoc (6.15.1)
+    rdoc (6.16.0)
       erb
       psych (>= 4.0.0)
       tsort
@@ -389,7 +389,7 @@ GEM
     stackprof (0.2.27)
     stimulus-rails (1.3.4)
       railties (>= 6.0.0)
-    stringio (3.1.7)
+    stringio (3.1.8)
     syntax (1.2.2)
     thor (1.4.0)
     thruster (0.1.16)