Link to the latest version of ftpext specification

Source commit: 4e4cf72291715fc7845d059545b7df1605b1d33d

source/core/FtpFileSystem.cpp

@@ -1035,7 +1035,7 @@ UnicodeString __fastcall TFTPFileSystem::DoCalculateFileChecksum(
   bool UsingHashCommand, const UnicodeString & Alg, TRemoteFile * File)
 {
   // Overview of server supporting various hash commands is at:
-  // https://tools.ietf.org/html/draft-ietf-ftpext2-hash-03#appendix-B
+  // https://tools.ietf.org/html/draft-bryan-ftpext-hash-02#appendix-B
 
   UnicodeString CommandName;