[NFC] Correcting test case for SR-11535 and adding a explanation comment

Author: LucianoPAlmeida

test/decl/enum/enumtest.swift

@@ -510,7 +510,10 @@ let _: GenericEnumWithStaticNone<Int>? = .none // expected-warning {{assuming yo
 // expected-note@-1 {{explicitly specify 'Optional' to silence this warning}}{{42-42=Optional}}
 // expected-note@-2 {{use 'GenericEnumWithStaticNone<Int>.none' instead}}{{42-42=GenericEnumWithStaticNone<Int>}}
 let _: GenericEnumWithStaticNone<String>? = .none // Okay
-let _: GenericEnumWithStaticNone? = .none // FIXME(SR-11535): This should be diagnosed
+
+let _: GenericEnumWithStaticNone? = .none // Okay
+// Base can only be inferred as static member `none` since `Optional.none` overload does not
+// provide a valid solution because the struct's generic argument `T` cannot be infered in this context.
 
 enum GenericEnumWithoutNone<T> {
   case a