Use original descriptor when mapping fake override

Otherwise wrong CONFLICTING_INHERITED_JVM_DECLARATIONS were reported

 #KT-10691 Fixed

compiler/testData/codegen/box/bridges/substitutionInSuperClass/differentErasureInSuperClass.kt

@@ -0,0 +1,15 @@
+public open class A<T> {
+    fun foo(x: T) = "O"
+    fun foo(x: A<T>) = "K"
+}
+
+// Shoudt not be reported CONFLICTING_INHERITED_JVM_DECLARATIONS
+class B : A<A<String>>()
+
+fun box(): String {
+    val x: A<String> = A()
+    val y: A<A<String>> = A()
+    val b = B()
+
+    return b.foo(x) + b.foo(y)
+}