fix(basti): remove redundant instance IAM policy

[BohdanPetryshyn]

Proposed Changes

This PR removes the s3:GetEncryptionConfiguration action from the bastion instance policy as it is redundant.

Related Issues/PRs

52

Checklist

• [x] I cleaned up my code.
• [x] All the tests and checks passed (npm run test).
• [x] I have added necessary documentation and/or updated existing documentation.
• [x] I have added or modified tests to cover the changes.