(kotlin) remove very old keywords and update example code (#2623)

Removes obsolete Kotlin keywords and updates example.

- These are no longer valid Kotlin keywords. (and there removal from the grammar was suggested years ago) 
- Also remove the `trait` usage from the example and format the code
  according to the Kotlin coding conventions.

Reference:
af601cb

CHANGES.md

@@ -7,9 +7,11 @@ New themes:
 Language Improvements:
 
 - enh(matlab) Add new R2019b `arguments` keyword and fix `enumeration` keyword (#2619) [Andrew Janke][]
+- fix(kotlin) Remove very old keywords and update example code (#2623) [kageru][]
 
 [Andrew Janke]: https://github.com/apjanke
 [Samia Ali]: https://github.com/samiaab1990
+[kageru]: https://github.com/kageru
 
 
 ## Version 10.1.1

src/languages/kotlin.js

@@ -14,9 +14,7 @@ export default function(hljs) {
       'crossinline dynamic final enum if else do while for when throw try catch finally ' +
       'import package is in fun override companion reified inline lateinit init ' +
       'interface annotation data sealed internal infix operator out by constructor super ' +
-      'tailrec where const inner suspend typealias external expect actual ' +
-      // to be deleted soon
-      'trait volatile transient native default',
+      'tailrec where const inner suspend typealias external expect actual',
     built_in:
       'Byte Short Char Int Long Boolean Float Double Void Unit Nothing',
     literal:

test/detect/kotlin/default.txt

@@ -1,12 +1,12 @@
 import kotlin.lang.test
 
-trait A {
+interface A {
     fun x()
 }
 
-fun xxx() : Int {
-	return 888
+fun xxx(): Int {
+    return 888
 }
 
-public fun main(args : Array<String>) {
+public fun main(args: Array<String>) {
 }