Remove unneeded logging from ZRLE decoder

We will log the exception, so avoid direct writes to stderr by
simply removing these log lines.

common/rfb/zrleDecode.h

             } while (b == 255);
 
             if (end - ptr < len) {
-              fprintf (stderr, "ZRLE decode error\n");
               throw Exception ("ZRLE decode error");
             }
 
               } while (b == 255);
 
               if (end - ptr < len) {
-                fprintf (stderr, "ZRLE decode error\n");
                 throw Exception ("ZRLE decode error");
               }
             }