Fix official SWE-Bench docker image prefix

[tchewik]

• This change is worth documenting at https://docs.all-hands.dev/
• Include this change in the Release Notes. If checked, you must provide an end-user friendly description for your change below

End-user friendly description of the problem this fixes or functionality that this introduces.

The correct Docker image prefix is applied when building official images. Previously, the system attempted to load non-existent xingyaoww/sweb.eval.* images instead of swebench/sweb.eval.*.

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Give a summary of what the PR does, explaining any non-trivial design decisions.

• Overrides the default prefix with the official repository prefix when building official SWE-Bench images.

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Link of any specific issues this addresses.

Fix #7168
Fix #7143

[xingyaoww]

Thanks!