Fix typo on 'Scale up on multiple devices' guide

[DavidUlloa6310]

What does this PR do?

This PR fixes a small typo found in the "Scale up on multiple devices" guide, where previously "If you are new parallelization in JAX" is written, but is replaced by "If you are new to parallelization in JAX". For an exact link to the issue found within the documentation, see the link here: https://flax.readthedocs.io/en/latest/guides/flax_gspmd.html#:~:text=If%20you%20are%20new%20parallelization%20in%20JAX.

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