build(deps): bump json from 2.15.1 to 2.15.2 in /assets/service_broker

Bumps [json](https://github.com/ruby/json) from 2.15.1 to 2.15.2.
- [Release notes](https://github.com/ruby/json/releases)
- [Changelog](https://github.com/ruby/json/blob/master/CHANGES.md)
- [Commits](ruby/json@v2.15.1...v2.15.2)

---
updated-dependencies:
- dependency-name: json
  dependency-version: 2.15.2
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

assets/service_broker/Gemfile.lock

@@ -3,7 +3,7 @@ GEM
   specs:
     base64 (0.3.0)
     diff-lcs (1.6.2)
-    json (2.15.1)
+    json (2.15.2)
     logger (1.7.0)
     mustermann (3.0.4)
       ruby2_keywords (~> 0.0.1)