KotlinQuickDocumentationProvider: fix quick doc for elements from type hierarchy

Fix quick doc for light classes

 #KT-7964 Fixed

idea/testData/kdoc/inTypeHierarchy/simple.kt

@@ -0,0 +1,8 @@
+package a.b.c
+
+/**
+ * Very special class
+ */
+class <caret>A {
+
+}