Add minimal comment // See PR #5968

Author: rwgk

include/pybind11/detail/common.h

@@ -87,7 +87,7 @@
 #    endif
 #endif
 
-#if defined(__cpp_lib_launder) && !(defined(_MSC_VER) && (_MSC_VER < 1920))
+#if defined(__cpp_lib_launder) && !(defined(_MSC_VER) && (_MSC_VER < 1920)) // See PR #5968
 #    define PYBIND11_STD_LAUNDER std::launder
 #    define PYBIND11_HAS_STD_LAUNDER 1
 #else