Userland: Prefer _short_string over String::from_utf8_short_string

This user-defined literal is a strictly equivalent but shorter alias to
`String::from_utf8_short_string`.

Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp

@@ -1142,7 +1142,7 @@ WebIDL::ExceptionOr<void> BrowsingContext::navigate(
         } else {
             // Otherwise let navigation id be the result of generating a random UUID. [UUID]
             // FIXME: Generate a UUID.
-            navigation_id = String::from_utf8_short_string("FIXME"sv);
+            navigation_id = "FIXME"_short_string;
         }
     }