Bump json from 2.7.6 to 2.9.1

Bumps [json](https://github.com/ruby/json) from 2.7.6 to 2.9.1.
- [Release notes](https://github.com/ruby/json/releases)
- [Changelog](https://github.com/ruby/json/blob/master/CHANGES.md)
- [Commits](ruby/json@v2.7.6...v2.9.1)

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

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

Gemfile.lock

@@ -37,7 +37,7 @@ GEM
     httpclient (2.8.3)
     i18n (1.10.0)
       concurrent-ruby (~> 1.0)
-    json (2.7.6)
+    json (2.9.1)
     kicker (3.0.0)
       listen (~> 1.3.0)
       notify (~> 0.5.2)