Update changelog for version 2.18

Changelog.md

 # Changelog
 
+## [2.18] - 2024-10-01
+-  Use solo pool for Celery workers
+
+## [2.17] - 2024-09-30
+- NOTHING IS HERE (JENKINS ISSUE)
+
+## [2.16] - 2024-09-30
+- NOTHING IS HERE (JENKINS ISSUE)
+
 ## [2.15] - 2024-09-30
 - Show current license usage when updating Kentik license of a router
 - Fix the bug of clearing all the AE members and creating new objects instead of updating it.