Fixed spelling

Author: WesleyJ-128

README.md

@@ -13,4 +13,4 @@ The screen will then show the name of the current mission across the top; and th
 * The bottom button recalibrates the gyro
 * The top button recalibrates the color sensor
 
-**When a mission is running, all buttons lose their normal functioon, and will abort the current mission.**
+**When a mission is running, all buttons lose their normal function, and will abort the current mission.**