docs: Update DISALLOW_CREATE_WINDOWS documentation so that it explains that...

docs: Update DISALLOW_CREATE_WINDOWS documentation so that it explains that windows besides app windows should not be created. This will block the creation of the following types of windows.

LayoutParams#TYPE_TOAST
LayoutParams#TYPE_APPLICATION_OVERLAY

Bug: 265840695
Change-Id: I12d36306aff17c3a289a0bd058a6e7a4d2217f22
Tests: built docs with go/abtd