usb: doc: Add note about cdc+dfu Windows OS exception.

Add a note for composite (CDC+DFU) device overlay.
Composite device CDC+DFU may not work with Windows OS host.
Windows OS does not send reset after DFU_DETACH request
(does not re-enumerates) and thus make it unable for
the device to restart in DFU mode.

For more details refer to #23337.

Signed-off-by: Emil Obalski <emil.obalski@nordicsemi.no>