Further cleanup of OS_MACOSX in net

Bug: 1105907
Change-Id: I2b7ab8c7671cbd492394d453a14fb47517dbc4d9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2328340
Auto-Submit: Avi Drissman <avi@chromium.org>
Commit-Queue: David Benjamin <davidben@chromium.org>
Reviewed-by: David Benjamin <davidben@chromium.org>
Cr-Commit-Position: refs/heads/master@{#793157}

net/socket/udp_socket_posix.cc

@@ -99,7 +99,7 @@ int GetIPv4AddressFromIndex(int socket, uint32_t index, uint32_t* address) {
   return OK;
 }
 
-#endif  // OS_MACOSX
+#endif  // OS_APPLE
 
 #if defined(OS_MAC)