docs: Documentation now prefers refrences over UDLs

docs/faq.rst

@@ -49,7 +49,7 @@ Why a dimensionless quantity is not just an fundamental arithmetic type?
 In the initial design of this library the resulting type of the division of
 two quantities was their common representation type::
 
-    static_assert(std::is_same_v<decltype(10_q_km / 5_q_km), std::int64_t>);
+    static_assert(std::is_same_v<decltype(10 * km / (5 * km)), std::int64_t>);
 
 The reasoning behind it was to not provide a false impression of a strong `quantity` type
 for something that looks and feels like a regular number. Also all of the mathematic