Bump orjson from 3.9.5 to 3.9.15 in /utils/plot_json_export

Bumps [orjson](https://github.com/ijl/orjson) from 3.9.5 to 3.9.15.
- [Release notes](https://github.com/ijl/orjson/releases)
- [Changelog](https://github.com/ijl/orjson/blob/master/CHANGELOG.md)
- [Commits](ijl/orjson@3.9.5...3.9.15)

---
updated-dependencies:
- dependency-name: orjson
  dependency-type: direct:production
...

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

utils/plot_json_export/requirements.txt

@@ -4,7 +4,7 @@ fonttools==4.42.1
 kiwisolver==1.4.5
 matplotlib==3.7.2
 numpy==1.25.2
-orjson==3.9.5
+orjson==3.9.15
 packaging==23.1
 Pillow==10.0.1
 pyparsing==3.0.9