fix(terraform): Fixed flaky test for CKV_AWS_356

[bo156]

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Description

Added setUp function to clear the cache before the test for CKV_AWS_356 as the cloudsplaining package uses a cache on the class level, making the test fail occasionally because it actually uses something wrong from the cache.

Checklist:

• My code follows the style guidelines of this project
• 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
• Any dependent changes have been merged and published in downstream modules