Update JAX integration proposal

[sandipanpanda]

What this PR does / why we need it:
A separate Coordinator replica for JAX is not needed, since Pod template will be the same and Worker with process_id 0 will act as the Coordinator.

• https://jax.readthedocs.io/en/latest/multi_process.html
• https://jax.readthedocs.io/en/latest/_autosummary/jax.distributed.initialize.html#jax-distributed-initialize

[sandipanpanda]

/cc @andreyvelich @tenzen-y
/area gsoc

[andreyvelich]

Related: #2145

[andreyvelich]

Thank you for updating this @sandipanpanda!
/lgtm
/approve

[google-oss-prow]

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[coveralls]

Pull Request Test Coverage Report for Build 9913473227

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.02%) to 35.406%

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Files with Coverage Reduction	New Missed Lines	%
pkg/controller.v1/mpi/mpijob_controller.go	2	81.05%

Totals
Change from base Build 9906458669:	-0.02%
Covered Lines:	4378
Relevant Lines:	12365

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💛 - Coveralls