Add changelog fragment for azeventhubs v2 upgrade

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: zmoog

changelog/fragments/1775080204-upgrade-azeventhubs-v2.yaml

@@ -0,0 +1,4 @@
+kind: upgrade
+summary: Upgrade Azure Event Hubs SDK (azeventhubs) from v1.3.1 to v2.0.2.
+pr: https://github.com/elastic/beats/pull/49867
+component: filebeat