iot/policy: Improve diffs of policy

[YakDriver]

Description

Relations

Relates #23288

References

Output from Acceptance Testing

% make testacc TESTS=TestAccIoTPolicy_ PKG=iot
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./internal/service/iot/... -v -count 1 -parallel 20 -run='TestAccIoTPolicy_'  -timeout 180m
=== RUN   TestAccIoTPolicy_basic
=== PAUSE TestAccIoTPolicy_basic
=== RUN   TestAccIoTPolicy_disappears
=== PAUSE TestAccIoTPolicy_disappears
=== CONT  TestAccIoTPolicy_basic
=== CONT  TestAccIoTPolicy_disappears
--- PASS: TestAccIoTPolicy_disappears (12.54s)
--- PASS: TestAccIoTPolicy_basic (16.96s)
PASS
ok  	github.com/hashicorp/terraform-provider-aws/internal/service/iot	18.694s

[github-actions]

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[github-actions]

This functionality has been released in v4.50.0 of the Terraform AWS Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

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[github-actions]

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