Update yml files to fix validation issues (removing references)

Author: jwindley

datasets/attack_techniques/T1553.001/atomic_red_team/macos_gatekeeper_bypass_xattr/macos_gatekeeper_bypass_xattr.yml

@@ -6,6 +6,4 @@ environment: vm
 datasets:
 - name: macos_gatekeeper_bypass_xattr.log
   path: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1553.001/atomic_red_team/macos_gatekeeper_bypass_xattr/
-  sourcetype: 'osquery:results'
-references:
-- https://www.atomicredteam.io/atomic-red-team/atomics/T1553.001
+  sourcetype: 'osquery:results'

datasets/attack_techniques/T1553.001/macos_gatekeeper_bypass_LSFileQuarantineEnabled/macos_gatekeeper_bypass_LSFileQuarantineEnabled.yml

@@ -6,6 +6,4 @@ environment: vm
 datasets:
 - name: macos_gatekeeper_bypass_LSFileQuarantineEnabled.log
   path: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1553.001/macos_gatekeeper_bypass_LSFileQuarantineEnabled/
-  sourcetypes: 'osquery:results'
-references:
-- https://attack.mitre.org/detectionstrategies/DET0288
+  sourcetypes: 'osquery:results'