Push Down: Do not specifiy visibility on generated overriding members

#KT-12971 Fixed

idea/testData/refactoring/pushDown/dropVisibilityOnGeneratedOverride.kt

@@ -0,0 +1,10 @@
+open class A {
+    // INFO: {"checked": "true", "toAbstract": "true"}
+    protected open fun foo() {
+
+    }
+}
+
+class B : A() {
+
+}

idea/testData/refactoring/pushDown/dropVisibilityOnGeneratedOverride.kt.after

@@ -0,0 +1,12 @@
+open class A {
+    // INFO: {"checked": "true", "toAbstract": "true"}
+    protected abstract fun foo()
+}
+
+class B : A() {
+    // INFO: {"checked": "true", "toAbstract": "true"}
+    override fun foo() {
+
+    }
+
+}