Use new sequence builders in tests

Coroutine tests will fail when LV=1.2 because there're no such builders
in kotlin.coroutines.experimental.

#KT-26678

compiler/testData/codegen/box/coroutines/controlFlow/kt22694.kt

@@ -5,7 +5,6 @@
 // COMMON_COROUTINES_TEST
 import helpers.*
 import COROUTINES_PACKAGE.*
-import COROUTINES_PACKAGE.intrinsics.*
 
 enum class Foo(vararg expected: String) {
     A("start", "A", "end"),
@@ -30,7 +29,7 @@ fun box(): String {
 }
 
 fun getSequence(a: Foo) =
-    buildSequence {
+    sequence {
         yield("start")
         when (a) {
             Foo.A -> {

compiler/testData/codegen/box/coroutines/suspendFunctionAsCoroutine/ifExpressionInsideCoroutine.kt

@@ -5,10 +5,9 @@
 // COMMON_COROUTINES_TEST
 import helpers.*
 import COROUTINES_PACKAGE.*
-import COROUTINES_PACKAGE.intrinsics.*
 
 val f = run {
-    buildSequence {
+    sequence {
         if (true) {
             yield("OK")
         }