style: format code with Ktlint

This commit fixes the style issues introduced in 98c91a1 according to the output
from Ktlint.

Details: None

src/test/kotlin/MarsRoverTests.kt

@@ -20,7 +20,7 @@ class MarsRoverTests {
         "1 2 S, M, 1 1 S",
         "1 2 W, M, 0 2 W",
         "1 2 N, LMLMLMLMM, 1 3 N",
-        "3 3 E, MMRMMRMRRM, 5 1 E"
+        "3 3 E, MMRMMRMRRM, 5 1 E",
     )
     fun `execute commands`(startingPosition: String, instructions: String, expectedOutput: String) {
         val rover = Rover(startingPosition)