chore: Move boto3 import for training sample

[ryansteakley]

Description of your changes:

• Boto3 import was below code that used boto3

Checklist:

• [x ] The title for your pull request (PR) should follow our title convention. Learn more about the pull request title convention used in this repository.

[google-oss-prow[bot]]

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[google-oss-prow[bot]]

Hi @ryansteakley. Thanks for your PR.

I'm waiting for a kubeflow member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[ryansteakley]

/ok-to-test