Improve readability of kotlin code (#1233)

* style(kotlin): Improve kotlin codes readability.

* remove redundant quotes.

codes/kotlin/chapter_dynamic_programming/climbing_stairs_dp.kt

@@ -27,9 +27,7 @@ fun climbingStairsDPComp(n: Int): Int {
     var a = 1
     var b = 2
     for (i in 3..n) {
-        val tmp = b
-        b += a
-        a = tmp
+        b += a.also { a = b }
     }
     return b
 }