fix sigma rule syntax issues

Author: adanalvarez

rules/cloud/aws/cloudtrail/aws_sts_getcalleridentity_trufflehog.yml

@@ -8,7 +8,6 @@ references:
     - https://github.com/trufflesecurity/trufflehog
 author: Adan Alvarez @adanalvarez
 date: 2025-10-12
-modified: 2025-10-12
 tags:
     - attack.discovery
     - attack.t1087.004
@@ -23,4 +22,4 @@ detection:
     condition: selection
 falsepositives:
     - Legitimate internal security scanning or key validation that intentionally uses TruffleHog. Authorize and filter known scanner roles, IP ranges, or assumed roles as needed.
-level: medium
+level: low