dts: boards: st, stm32f3_disco: update user button logic

Updated the stm32f3_disco board user button logic from
active low to active high as per datasheet.

Signed-off-by: Muhammad Waleed Badar <walid.badar@gmail.com>

boards/st/stm32f3_disco/stm32f3_disco.dts

@@ -61,7 +61,7 @@
 		compatible = "gpio-keys";
 		user_button: button {
 			label = "User";
-			gpios = <&gpioa 0 GPIO_ACTIVE_LOW>;
+			gpios = <&gpioa 0 GPIO_ACTIVE_HIGH>;
 			zephyr,code = <INPUT_KEY_0>;
 		};
 	};