Add known issue for AWS S3 input (target 8.15) (#41733)

CHANGELOG.asciidoc

@@ -231,6 +231,19 @@ https://github.com/elastic/beats/compare/v8.14.3\...v8.15.0[View commits]
 
 - The Azure EventHub input in Filebeat is not found when running on Windows. Please refrain from upgrading to 8.15. See {issue}40608[40608] for details.
 - Memory usage is not correctly limited by the number of events actively in the memory queue, but rather the maximum size of the memory queue regardless of usage. {issue}41355[41355]
+*Filebeat*
+- The AWS S3 input polling mode is not working when the S3 bucket is not in the `us-east-1` default region. This also impacts all AWS integrations and any custom AWS log integration which uses the `aws-s3` input polling mode. When using Filebeat, please add a `default_region` configuration with the region of the S3 bucket. For example:
++
+["source","yaml"]
+----
+filebeat.inputs:
+- type: aws-s3
+  enabled: true
+  credential_profile_name: elastic-observability
+  default_region: us-east-2
+  number_of_workers: 5
+  bucket_arn: 'arn:aws:s3:::test1'
+----
 
 *Metricbeat*