Fix parse of commodity namespace from scheme istream.

Just ignore 2 instead of ignoring 1 twice. No ifdef required.

libgnucash/app-utils/gnc-option-impl.hpp

@@ -414,14 +414,10 @@ gnc_option_from_scheme (std::istream& iss, OptType& opt)
         {
             iss.ignore(strlen(commodity_scm_intro) + 1, '"');
             std::getline(iss, name_space, '"');
- // libc++ doesn't consume the end character, libstdc++ does
-#ifdef _LIBCPP_VERSION
-            iss.ignore(1, '"');
-#endif
         }
         else
             name_space = GNC_COMMODITY_NS_CURRENCY;
-        iss.ignore(1, '"');
+        iss.ignore(2, '"');
         std::getline(iss, mnemonic, '"');
 
         if (type == GncOptionUIType::COMMODITY)