Fix problem with Windows version check

Author: yhirose

httplib.h

@@ -27,7 +27,7 @@
 #endif
 
 #ifdef _WIN32
-#if defined(_WIN32_WINNT) && _WIN32_WINNT < 0x0602
+#if defined(_WIN32_WINNT) && _WIN32_WINNT < 0x0A00
 #error                                                                         \
     "cpp-httplib doesn't support Windows 8 or lower. Please use Windows 10 or later."
 #endif