To elaborate on Andrew's response, if you don't use FortiClient or FortiAP, you can disable (depending on your FortiGate firmware version) either disable FortiTelemetry or Security Fabric (which is FortiTelemetry and CAPWAP bundled) on the interface(s). If you do use FortiAPs for wireless stuff, and only have the Security Fabric option, you can't disable it. In that case a local-in policy as Andrew advised is your best option.
+++ Divide by Cucumber Error. Please Reinstall Universe and Reboot +++