Fixed ShortenReferences for extension on companion object

idea/testData/shortenRefs/extensionForCompanionObject.dependency.kt

@@ -0,0 +1,8 @@
+package dependency
+
+class AClass {
+    companion object {
+    }
+}
+
+fun AClass.Companion.extFun(){}

idea/testData/shortenRefs/extensionForCompanionObject.kt

@@ -0,0 +1,5 @@
+import dependency.extFun
+
+fun foo() {
+    <selection>dependency.AClass.extFun()</selection>
+}

idea/testData/shortenRefs/extensionForCompanionObject.kt.after

@@ -0,0 +1,6 @@
+import dependency.AClass
+import dependency.extFun
+
+fun foo() {
+    AClass.extFun()
+}