QRandom: drop a usage of std::is_literal_type

It's deprecated/removed, and indeed doesn't check anything that it's
not also already being checked by the previous line.

Change-Id: Ic80ca43f390dd989ced69f196efa7313069e7c6d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 6351b5433da083890e47faa62e21fb40fd042c79)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/global/qrandom.cpp

@@ -373,7 +373,6 @@ struct QRandomGenerator::SystemAndGlobalGenerators
 
         constexpr SystemAndGlobalGenerators g = {};
         Q_UNUSED(g);
-        static_assert(std::is_literal_type<SystemAndGlobalGenerators>::value);
 #endif
     }