src/network/protocols/ranking.hpp: add missing <stdint.h> include (#5346)

Without the chnage the build fails on upcoming `gcc-15` as:

    /build/source/src/network/protocols/ranking.hpp:31:5: error: 'uint32_t' does not name a type
       31 |     uint32_t online_id;
          |     ^~~~~~~~

Author: trofi

src/network/protocols/ranking.hpp

@@ -22,6 +22,7 @@
 #include <map>
 #include <memory>
 #include <vector>
+#include <stdint.h>
 
 class XMLNode;
 class NetworkPlayerProfile;