Use static_assert in handleFromVariant

Author: eltoder

ql/quote.cpp

@@ -32,7 +32,7 @@ namespace QuantLib {
                 } else if constexpr (std::is_same_v<T, Handle<Quote>>) {
                     return x;
                 } else {
-                    QL_FAIL("Unexpected type in quote variant");
+                    static_assert(false, "Unexpected type in quote variant");
                 }
             },
             value);