unshallow git history prior to pushing (#3479)

## Motivation and Context
I'm not sure what changed but I was able to reproduce the failure from
https://github.com/smithy-lang/smithy-rs/actions/runs/8242141624/job/22564640708
with the downloaded release artifact. Because the clone was shallow, git
did not attempt to push because the histories were unrelated.

Of course, they are in reality, but because the history is shallow git
doesn't know that.

I verified this allowed a dry run push to succeed locally.

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