Don't pass the --setup_file option when a package is already installed in the custom image.

[tvalentyn]

Description

Fixes https://stackoverflow.com/questions/78218949/how-to-pre-build-worker-container-dataflow-insights-sdk-worker-container-imag

Checklist

• [x ] I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• [ x] README is updated to include all relevant information
• [x ] Tests pass: nox -s py-3.9 (see Test Environment Setup)
• [ x] Lint pass: nox -s lint (see Test Environment Setup)
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• [x ] Please merge this PR for me once it is approved

[tvalentyn]

R: @davidcavazos

[francocalvo]

This might be breaking something.
I created a pipeline almost the same as the example and it wouldn't work up until I added the flag again.