Typo fix

maps_extended.proto

@@ -12,10 +12,10 @@ service MapsService {
   rpc Delete(MapId) returns (NullResponse);
   rpc List(ListRequest) returns (MapList);
   rpc IncrementLoadCount(MapId) returns (NullResponse);
-  rpc GetSnmfDownloadUrl(MapId) returns (SnmfDownloadUrl);
+  rpc GetSnfmDownloadUrl(MapId) returns (SnfmDownloadUrl);
 }
 
-message SnmfDownloadUrl { string Url = 1; }
+message SnfmDownloadUrl { string Url = 1; }
 
 message MapIdList { repeated int64 ID = 1; }