Update tcp_client.h

include/spdlog/details/tcp_client.h

@@ -4,7 +4,7 @@
 #pragma once
 
 #ifdef _WIN32
-#error tcp_client not supported under windows yet
+#error include tcp_client-windows.h instead
 #endif
 
 // tcp client helper
@@ -146,4 +146,4 @@ public:
     }
 };
 } // namespace details
-} // namespace spdlog
+} // namespace spdlog