chore(deps): bump python-rapidjson from 1.20 to 1.21

Bumps [python-rapidjson](https://github.com/python-rapidjson/python-rapidjson) from 1.20 to 1.21.
- [Changelog](https://github.com/python-rapidjson/python-rapidjson/blob/master/CHANGES.rst)
- [Commits](python-rapidjson/python-rapidjson@v1.20...v1.21)

---
updated-dependencies:
- dependency-name: python-rapidjson
  dependency-version: '1.21'
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

ft_client/requirements.txt

@@ -1,3 +1,3 @@
 # Requirements for freqtrade client library
 requests==2.32.4
-python-rapidjson==1.20
+python-rapidjson==1.21

requirements.txt

@@ -28,7 +28,7 @@ rich==14.0.0
 pyarrow==20.0.0; platform_machine != 'armv7l'
 
 # Load ticker files 30% faster
-python-rapidjson==1.20
+python-rapidjson==1.21
 # Properly format api responses
 orjson==3.10.18