[Fix bug] always run prepare-test-spec

[yangw-dev]

Follow up with #8125

Example of failed benchmark run: https://github.com/pytorch/executorch/actions/runs/13666476394

We made prepare-test-spec have dependency on export-model, it seems like when there is any failure happens in the export model step, it will skip the whole prepare-test-spec. We want to always run prepare-test-spec.

in step prepare-test-spec, we will check wether the export-model successfully build the model, if not, no test-spec will be uploaded. This makes the final step mobile-on-device step fails early at verify-test-spec part

[pytorch-bot]

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⏳ No Failures, 3 Pending

As of commit 71e0775 with merge base 5ac4a3c ():
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[huydhn]

Oops, I think we should revert #8482 instead because having always() here will negate #8482. In hindsight, we shouldn't make prepare-test-spec depend on export-models. I forgot to tell you that the issue #8125 has been fixed by #8786 (I did it last minute before signing off on Thursday, my bad)

[yangw-dev]

got it!