[Docs] `System.processCPUUsage` not documented

[itlancer]

Problem Description

System.processCPUUsage getter not documented.

Related issues:
https://tracker.adobe.com/#/view/FP-4198415
#3720

Steps to Reproduce

https://airsdk.dev/reference/actionscript/3.0/flash/system/System.html

Actual Result:
System.processCPUUsage getter not documented.

Expected Result:
System.processCPUUsage shout be documented or removed.