Update fastjsonschema requirement from ~=2.17.1 to ~=2.21.0 in /tests

Updates the requirements on [fastjsonschema](https://github.com/horejsek/python-fastjsonschema) to permit the latest version.
- [Changelog](https://github.com/horejsek/python-fastjsonschema/blob/master/CHANGELOG.txt)
- [Commits](horejsek/python-fastjsonschema@v2.17.1...v2.21.0)

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

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

tests/constraints.txt

@@ -10,7 +10,7 @@ scipy>=1.11.1; python_version >= "3.9"
 sympy>=1.10
 wheel>=0.38.1
 defusedxml>=0.7.1
-fastjsonschema~=2.17.1
+fastjsonschema~=2.21.0
 tensorflow>=2.5,<2.19.0
 requests>=2.25.1
 opencv-python>=4.5