JS: bound callable references (KT-13573).

compiler/testData/codegen/box/callableReference/bound/kt12738.kt

@@ -1,6 +1,5 @@
-// TODO: muted automatically, investigate should it be ran for JS or not
+// Enable when callable references to builtin members is supported
 // IGNORE_BACKEND: JS
-
 fun <T> get(t: T): () -> String {
     return t::toString
 }