Update copyright.

Change the copyright from "JetBrains s.r.o." to
"JetBrains s.r.o. and Kotlin Project contributors"
Update TestGenerator.kt

generators/test-generator/tests/org/jetbrains/kotlin/generators/tests/generator/TestGenerator.kt

@@ -52,8 +52,8 @@ class TestGenerator(
         val year = GregorianCalendar()[Calendar.YEAR]
         p.println(
             """/*
-            | * Copyright 2010-$year JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
-            | * that can be found in the license/LICENSE.txt file.
+            | * Copyright 2010-$year JetBrains s.r.o. and Kotlin Programming Language contributors.
+            | * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
             | */
             |""".trimMargin()
         )