fix(aws): exclude member accounts in IAM Root Credentials check

[MrCloudSec]

Context

The recently added check iam_root_credentials_management_enabled uses the ListOrganizationsFeatures API to verify if centralized root credentials management is enabled. However, this API is restricted to the management account or delegated administrators. AWS Support confirmed that member accounts cannot access this information, resulting in the AccountNotManagementOrDelegatedAdministratorException error.

Description

The check now skips findings for member accounts, as they are unable to retrieve the required data due to API restrictions. This ensures accurate results without unnecessary findings for member accounts.

Checklist

• Are there new checks included in this PR? Yes / No
  • If so, do we need to update permissions for the provider? Please review this carefully.
• Review if the code is being covered by tests.
• Review if code is being documented following this specification https://github.com/google/styleguide/blob/gh-pages/pyguide.md#38-comments-and-docstrings
• Review if backport is needed.

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Attention: Patch coverage is 62.50000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 89.87%. Comparing base (572d5a1) to head (50e7597).
Report is 9 commits behind head on master.

Files with missing lines	Patch %	Lines
prowler/providers/aws/services/iam/iam_service.py	40.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5813      +/-   ##
==========================================
- Coverage   89.91%   89.87%   -0.04%     
==========================================
  Files        1133     1133              
  Lines       35308    35313       +5     
==========================================
- Hits        31747    31739       -8     
- Misses       3561     3574      +13     

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