Unused symbol: remove forced "used" from actual declarations

Now we really check whether actual declaration has usages
(in expect or actual code) or not
Related to KT-17512
Related to KT-15666

idea/testData/multiModuleQuickFix/safeDeleteFromActual/common/common.kt

@@ -0,0 +1,4 @@
+expect class My constructor() {
+    // TODO: also should be deleted (KT-15666)
+    fun foo()
+}

idea/testData/multiModuleQuickFix/safeDeleteFromActual/common/common.kt.after

@@ -0,0 +1,4 @@
+expect class My constructor() {
+    // TODO: also should be deleted (KT-15666)
+    fun foo()
+}