fix(terraform): prevent crash in S3AllowsAnyPrincipal with unparsed v…

[marcoHosseini]

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

Description

This PR fixes a parser crash in the CKV_AWS_70 (S3AllowsAnyPrincipal) check when it encounters an unparsed Terraform variable within a concat statement for an S3 Bucket Policy.

A TypeError was previously thrown when the parser expected a dictionary but received a string (the unparsed variable placeholder). I added an isinstance guard inside the loop to safely skip non-dictionary elements, along with a corresponding Terraform test fixture to prevent regression.

Fixes #7571

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my feature, policy, or fix is effective and works
• New and existing tests pass locally with my changes