Pass-thru other panw.panos log types

This removes the drop processor from the ingest node pipeline that drops events other than THREAT and TRAFFIC.
This way we can retain the other log data but don't necessarily handle the parsing of it.

Closes #16815

CHANGELOG.next.asciidoc

@@ -412,6 +412,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Explicitly set ECS version in all Filebeat modules. {pull}19198[19198]
 - Add new mode to multiline reader to aggregate constant number of lines {pull}18352[18352]
 - Add automatic retries and exponential backoff to httpjson input. {pull}18956[18956]
+- Changed the panw module to pass through (rather than drop) message types other than threat and traffic. {issue}16815[16815] {pull}19375[19375]
 
 *Heartbeat*
 

x-pack/filebeat/module/panw/panos/ingest/pipeline.yml

@@ -197,8 +197,6 @@ processors:
        - intrusion_detection
        - network
      if: 'ctx?._temp_?.message_type == "THREAT"'
- - drop:
-     if: 'ctx?.event?.category == null'
  - append:
      field: event.type
      value: allowed