Mark required call with 'caret' in abstract resolved calls test

compiler/testData/resolvedCalls/realExamples/stringPlusInBuilders.kt

@@ -1,5 +1,3 @@
-// !CALL: +
-
 trait Element {
     fun render(builder: StringBuilder, indent: String)
 }
@@ -34,7 +32,7 @@ fun html(init: HTML.() -> Unit): HTML = fail
 fun result() =
         html {
             head {
-                title {+"Foo"}
+                title { <caret>+"Foo" }
             }
         }