Do not show doc-comment references in data flow

idea/testData/slicer/outflow/docCommentRefs2.kt

@@ -0,0 +1,11 @@
+// FLOW: OUT
+
+val String.<caret>foo: Int
+    get() = 10
+
+/**
+ * Uses [foo]
+ */
+fun bar() {
+    val v = "".foo
+}