Updated build.gradle to target Kotlin 1.3.61

Author: MrMatthewLayton

build.gradle

@@ -1,7 +1,7 @@
 buildscript {
     ext {
         kotlin_group = "org.jetbrains.kotlin"
-        kotlin_version = "1.2.71"
+        kotlin_version = "1.3.61"
 
         junit_group = "org.junit.jupiter"
         junit_version = "5.3.1"