False positive removed in replace single line let intention #KT-14791 Fixed

idea/testData/intentions/replaceSingleLineLetIntention/assignment.kt

@@ -0,0 +1,8 @@
+// IS_APPLICABLE: false
+// WITH_RUNTIME
+
+fun withAssign(arg: String?): String {
+    var result: String = ""
+    arg?.let<caret> { result = it }
+    return result
+}