Bump json from 2.13.2 to 2.15.0 in the ruby-dependencies group (heroku#1648)

Bumps the ruby-dependencies group with 1 update: [json](https://github.com/ruby/json).


Updates `json` from 2.13.2 to 2.15.0
- [Release notes](https://github.com/ruby/json/releases)
- [Changelog](https://github.com/ruby/json/blob/master/CHANGES.md)
- [Commits](ruby/json@v2.13.2...v2.15.0)

---
updated-dependencies:
- dependency-name: json
  dependency-version: 2.15.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
  dependency-group: ruby-dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -21,7 +21,7 @@ GEM
       rrrretry (~> 1)
       thor (~> 1)
       threaded (~> 0)
-    json (2.13.2)
+    json (2.15.0)
     logger (1.7.0)
     moneta (1.0.0)
     multi_json (1.17.0)