dt-bindings: net: bluetooth: realtek: Fix uart-has-rtscts example

uart-has-rtscts is a boolean property. These are defined as present
(which means that this property evaluates to "true") or absent (which
means that this property evaluates to "false"). Remove the numeric value
from the example to make it comply with the boolean property bindings.

Fixes: 1cc2d0e0

 ("dt-bindings: net: bluetooth: Add rtl8723bs-bluetooth")
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>