Bump orjson from 3.8.9 to 3.9.15

Bumps [orjson](https://github.com/ijl/orjson) from 3.8.9 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@3.8.9...3.9.15)

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

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

requirements.txt

@@ -61,7 +61,7 @@ numpy==1.24.2
 openstep-plist==0.3.0.post1
 opentype-sanitizer==9.0.0
 opentypespec==1.9.1
-orjson==3.8.9
+orjson==3.9.15
 outcome==1.2.0
 packaging==23.0
 picosvg==0.20.6