Bump ujson from 4.0.2 to 5.1.0 in /frameworks/Python/flask (#7058)

Bumps [ujson](https://github.com/ultrajson/ultrajson) from 4.0.2 to 5.1.0.
- [Release notes](https://github.com/ultrajson/ultrajson/releases)
- [Commits](https://github.com/ultrajson/ultrajson/compare/4.0.2...5.1.0)

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

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

frameworks/Python/flask/requirements-pypy.txt

@@ -11,4 +11,4 @@ MarkupSafe==2.0.1
 meinheld==1.0.2
 uWSGI==2.0.19.1
 Werkzeug==2.0.1
-ujson==4.0.2
+ujson==5.1.0

frameworks/Python/flask/requirements.txt

@@ -12,5 +12,5 @@ MarkupSafe==2.0.1
 meinheld==1.0.2
 uWSGI==2.0.19.1
 Werkzeug==2.0.1
-ujson==4.0.2
+ujson==5.1.0
 orjson==3.6.0