[JS TESTS] Drop ES6 tests

compiler/tests-common-new/tests/org/jetbrains/kotlin/test/directives/JsEnvironmentConfigurationDirectives.kt

@@ -240,11 +240,6 @@ object JsEnvironmentConfigurationDirectives : SimpleDirectivesContainer() {
         applicability = DirectiveApplicability.File
     )
 
-    val RUN_ES6_MODE by directive(
-        description = "",
-        applicability = DirectiveApplicability.Global
-    )
-
     val PER_MODULE by directive(
         description = "",
         applicability = DirectiveApplicability.Global

compiler/tests-common-new/tests/org/jetbrains/kotlin/test/services/configuration/JsEnvironmentConfigurator.kt

@@ -232,7 +232,6 @@ class JsEnvironmentConfigurator(testServices: TestServices) : EnvironmentConfigu
 
         val libraries = when (module.targetBackend) {
             null -> JsConfig.JS_STDLIB + JsConfig.JS_KOTLIN_TEST
-            TargetBackend.JS_IR_ES6 -> dependencies
             TargetBackend.JS_IR -> dependencies
             TargetBackend.JS -> JsConfig.JS_STDLIB + JsConfig.JS_KOTLIN_TEST + dependencies
             else -> error("Unsupported target backend: ${module.targetBackend}")