Fix incorrect documentation about unblock_rules_using_execution_policies
What does this MR do and why?
Fix incorrect documentation about unblock_rules_using_execution_policies. We're evaluating the scans enforced for source branch: https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/app/services/security/security_orchestration_policies/policy_rule_evaluation_service.rb#L149.
References
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Related to #585752
Edited by Martin Cavoj