0.2.1: Increment version number for JAX-CFD

I would like to issue a new release to fix issues like
https://github.com/google/jax-cfd/issues/226

PiperOrigin-RevId: 632484011

0.2.0

0.2.0

0.1.0: [JAX-CFD] tweak installation & tests

The tweaks to the test suite ensure everything passes on my local
installation on my MacBook, and shave a few minutes off the execution
time.

If the README instructions are followed, the whole test-suite runs in about
two and a half minutes on my Mac. It excludes the "validation tests", which
are too slow to run on CPU.

PiperOrigin-RevId: 374442976