Update jax requirement from <=0.4.14 to <=0.4.21 in /tests

Updates the requirements on [jax](https://github.com/google/jax) to permit the latest version.
- [Release notes](https://github.com/google/jax/releases)
- [Changelog](https://github.com/google/jax/blob/main/CHANGELOG.md)
- [Commits](https://github.com/google/jax/compare/jaxlib-v0.1.32...jax-v0.4.21)

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

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

tests/constraints.txt

@@ -22,6 +22,6 @@ pytest>=5.0,<7.5
 pytest-dependency==0.5.1
 pytest-html==4.1.1
 pytest-timeout==2.1.0
-jax<=0.4.14
+jax<=0.4.21
 jaxlib<=0.4.14
 torch>=1.13,<2.2