efs/file_system_policy: Fix diffs with equivalent policies

[YakDriver]

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Relates #21968
Fixes #19245

Output from acceptance testing (us-west-2):

% make testacc TESTS=TestAccEFSFileSystemPolicy PKG=efs                            
TF_ACC=1 go test ./internal/service/efs/... -v -count 1 -parallel 20 -run='TestAccEFSFileSystemPolicy' -timeout 180m
--- PASS: TestAccEFSFileSystemPolicy_disappears (26.35s)
--- PASS: TestAccEFSFileSystemPolicy_equivalentPolicies (35.35s)
--- PASS: TestAccEFSFileSystemPolicy_equivalentPoliciesIAMPolicyDoc (35.53s)
--- PASS: TestAccEFSFileSystemPolicy_basic (41.84s)
--- PASS: TestAccEFSFileSystemPolicy_policyBypass (41.84s)
PASS
ok  	github.com/hashicorp/terraform-provider-aws/internal/service/efs	43.510s

Output from acceptance testing (GovCloud):

% make testacc TESTS=TestAccEFSFileSystemPolicy PKG=efs                            
TF_ACC=1 go test ./internal/service/efs/... -v -count 1 -parallel 20 -run='TestAccEFSFileSystemPolicy' -timeout 180m
--- PASS: TestAccEFSFileSystemPolicy_disappears (29.98s)
--- PASS: TestAccEFSFileSystemPolicy_equivalentPolicies (42.54s)
--- PASS: TestAccEFSFileSystemPolicy_equivalentPoliciesIAMPolicyDoc (42.64s)
--- PASS: TestAccEFSFileSystemPolicy_policyBypass (51.10s)
--- PASS: TestAccEFSFileSystemPolicy_basic (51.10s)
PASS
ok  	github.com/hashicorp/terraform-provider-aws/internal/service/efs	52.786s

[github-actions]

This functionality has been released in v3.69.0 of the Terraform AWS Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions]

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