Only #include <stdfloat> on MSVC when in C++23 mode to remove a warni…

…ng (#930)

* Only #include <stdfloat> on MSVC when in C++23 mode to remove a warning

The __has_include test for <stdfloat> returns true even in C++20 because the file exists, but the stdfloat header emits an error when not compiled with C++23.

Fixes #929

* Simplified condition for #including <stdfloat> thanks to gregmarr

include/cpp2util.h

@@ -196,7 +196,9 @@
         #endif
         #include <stdexcept>
         #if __has_include(<stdfloat>)
-            #include <stdfloat>
+            #if !defined(_MSC_VER) || _HAS_CXX23
+                #include <stdfloat>
+            #endif
         #endif
         #ifdef __cpp_lib_jthread
             #include <stop_token>