Update kotlin library to 1.3.72 (#1542)

Author: rlazo

build.gradle

@@ -15,7 +15,7 @@
 import com.google.firebase.gradle.plugins.license.LicenseResolverPlugin
 
 buildscript {
-    ext.kotlinVersion = '1.3.61'
+    ext.kotlinVersion = '1.3.72'
     repositories {
         google()
         jcenter()