K2: Update substituted member candidate if it contains type variables

See the comment at updateSubstitutedMemberIfReceiverContainsTypeVariable

It became necessary after delegate inference is rewritten, since before
that happened, stub types were being left there and FIR2IR handled
them accidentally properly because stub types are equal to anything.

But that wasn't really correct even there because stub types are not
intended to leak out of the FIR

^KT-61060

compiler/testData/codegen/box/delegatedProperty/noTypeVariablesLeft.kt

@@ -0,0 +1,18 @@
+import kotlin.reflect.KProperty
+
+var foo: (() -> String)? by property(null)
+
+private fun <T> property(initialValue: T): RwProperty<T> = RwProperty(initialValue)
+
+class RwProperty<V>(var v: V) {
+    operator fun getValue(thisRef: Any?, property: KProperty<*>): V = v
+
+    operator fun setValue(thisRef: Any?, property: KProperty<*>, value: V) {
+        this.v = value
+    }
+}
+
+fun box(): String {
+    foo = { "OK" }
+    return foo!!.invoke()
+}