add [[maybe_unused]] attribute to prevent innocuous warning

Signed-off-by: hultonha <hultonha@amazon.co.uk>

Code/Framework/AzCore/AzCore/Debug/Trace.h

@@ -127,7 +127,7 @@ namespace AZ
     #define AZ_TraceFmtCompileTimeCheck(expression, isVaArgs, baseMsg, msg, msgVargs)                                                                                                 \
     {                                                                                                                                                                                 \
         using namespace AZ::TraceInternal;                                                                                                                                            \
-        const auto& rTraceFmtCompileTimeCheckExpressionHelper = (expression); /* This is needed for edge cases for expressions containing lambdas, that were unsupported before C++20 */   \
+        [[maybe_unused]] const auto& rTraceFmtCompileTimeCheckExpressionHelper = (expression); /* This is needed for edge cases for expressions containing lambdas, that were unsupported before C++20 */   \
         constexpr ExpressionValidResult isValidTraceFmtResult = ExpressionIsValid<decltype(rTraceFmtCompileTimeCheckExpressionHelper)>::value;                                        \
         /* Assert different message depending whether it's const char array or if we have extra arguments */                                                                          \
         static_assert(!(isVaArgs) ? isValidTraceFmtResult != ExpressionValidResult::Invalid_ConstCharArray : true, baseMsg " " msg);                                                    \