Remove old buildIterator import (KT-26679)

idea/testData/quickfix/obsoleteCoroutines/buildIteratorImport.kt

@@ -0,0 +1,9 @@
+// "Fix experimental coroutines usage" "true"
+// ERROR: Using 'buildIterator(noinline suspend SequenceScope<T>.() -> Unit): Iterator<T>' is an error. Use 'iterator { }' function instead.
+// WITH_RUNTIME
+import kotlin.coroutines.<caret>experimental.buildIterator
+
+fun main(args: Array<String>) {
+    val lazySeq = buildIterator<Int> {
+    }
+}

idea/testData/quickfix/obsoleteCoroutines/buildIteratorImport.kt.after

@@ -0,0 +1,8 @@
+// "Fix experimental coroutines usage" "true"
+// ERROR: Using 'buildIterator(noinline suspend SequenceScope<T>.() -> Unit): Iterator<T>' is an error. Use 'iterator { }' function instead.
+// WITH_RUNTIME<caret>
+
+fun main(args: Array<String>) {
+    val lazySeq = buildIterator<Int> {
+    }
+}