Input: amijoy - fix grammar in documentation

Make small grammar fixes to Amiga joystick documentation.

Signed-off-by: George Anthony Vernon <contact@gvernon.com>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Link: https://lore.kernel.org/r/20250526135957.180254-4-contact@gvernon.com


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>