Join with assignment: fix false negative when local variable are used

#KT-34270 Fixed

idea/testData/intentions/joinDeclarationAndAssignment/usedLocal3.kt

@@ -0,0 +1,8 @@
+class Test(height: Int, width: Int) {
+    private val size: Int = height * width
+    private val <caret>data: Int
+
+    init {
+        data = size
+    }
+}