Update references to JAX's GitHub repo

JAX has moved from https://github.com/google/jax to https://github.com/jax-ml/jax

PiperOrigin-RevId: 702886838

Author: jakeharmon8

README.md

@@ -1,6 +1,6 @@
 # Mctx: MCTS-in-JAX
 
-Mctx is a library with a [JAX](https://github.com/google/jax)-native
+Mctx is a library with a [JAX](https://github.com/jax-ml/jax)-native
 implementation of Monte Carlo tree search (MCTS) algorithms such as
 [AlphaZero](https://deepmind.com/blog/article/alphazero-shedding-new-light-grand-games-chess-shogi-and-go),
 [MuZero](https://deepmind.com/blog/article/muzero-mastering-go-chess-shogi-and-atari-without-rules), and