Maxtext GPU test now point to image built using mode=stable

[parambole]

Description

Since JStS image is not yet publicly released reverting changes so that maxtext gpu test now point to image which is built using mode=stable

ref: AI-Hypercomputer/maxtext#1173

Checklist

Before submitting this PR, please make sure (put X in square brackets):

• I have performed a self-review of my code.
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• I have run one-shot tests and provided workload links above if applicable.
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[yangyuwei]

Thanks Param for the quick fix!

I think it's better to hold on merging this PR until AI-Hypercomputer/maxtext#1173 is merged and executed, otherwise, there will be no stable docker images that can be used by XLML tests.

In addition, it'd be great if you could run the tests to verify after the new stable docker image gets uploaded.

Does it make sense?