Fix the permadiff issue related to aws creds in resource_storage_transfer_job.

[googlyrahman]

Fix the permadiff issue related to aws creds in resource_storage_transfer_job, Closes hashicorp/terraform-provider-google#11535

Release Note Template for Downstream PRs (will be copied)

storagetransfer: fixed a permadiff with `transfer_spec.0.aws_s3_data_source.0.aws_access_key` `resource_storage_transfer_job`

[github-actions]

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[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

google provider: Diff ( 1 file changed, 1 insertion(+), 2 deletions(-))
google-beta provider: Diff ( 1 file changed, 1 insertion(+), 2 deletions(-))

[modular-magician]

Tests analytics

Total tests: 11
Passed tests: 11
Skipped tests: 0
Affected tests: 0

Click here to see the affected service packages

• storagetransfer

$\textcolor{green}{\textsf{All tests passed!}}$ View the [build log](https://storage.cloud.google.com/ci-vcr-logs/beta/refs/heads/auto-pr-10672/artifacts/82e28038-045a-4d6e-9b7f-e7a8b2c46700/build-log/replaying_test.log)

[github-actions]

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