[feat] relax memory capacity unbalance check constraint to 30%

[ocss884]

Motivation

As we are integrating SGLang to training framework like veRL. Current unbalance constraint 10% is too thight and could cause the SGLang engine initialization fail. For example, the ray header would occupy more memory on one worker than others and makes the unbalance check fail.

Modifications

Checklist

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[hnyls2002]

#5426 I think after this PR is merged, you can just diable the check in env.