dt-bindings: serial: rsci: Drop "uart-has-rtscts: false"

Drop "uart-has-rtscts: false" from binding as the IP supports hardware
flow control on all SoCs.

Cc: [e-mail]
Fixes: 25422e8f46c1 ("dt-bindings: serial: Add compatible for Renesas RZ/T2H SoC in sci")
Acked-by: Conor Dooley <[e-mail]>
Reviewed-by: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Biju Das <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/serial/renesas,rsci.yaml

···
   power-domains:
     maxItems: 1
 
-  uart-has-rtscts: false
-
 required:
   - compatible
   - reg