Update orjson requirement from ==3.8.*,>=3.8.6 to ==3.9.*

Updates the requirements on [orjson](https://github.com/ijl/orjson) to permit the latest version.
- [Release notes](https://github.com/ijl/orjson/releases)
- [Changelog](https://github.com/ijl/orjson/blob/master/CHANGELOG.md)
- [Commits](ijl/orjson@3.8.6...3.9.7)

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

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -1,4 +1,4 @@
 nextcord[speed, voice]  == 2.6.*
-orjson                  >=  3.8.6,  == 3.8.*
+orjson                  == 3.9.*
 aiohttp                 >=  3.8.4,  == 3.8.*
 GitPython               ==  3.1.30