fix skip unknown WireType.FIXED_64BIT value bug

Author: marsqing

protobuf/src/main/java/com/fasterxml/jackson/dataformat/protobuf/ProtobufParser.java

@@ -954,7 +954,7 @@ private void _skipUnknownValue(int wireType) throws IOException
             _skipBytes(4);
             break;
         case WireType.FIXED_64BIT:
-            _skipBytes(64);
+            _skipBytes(8);
             break;
         case WireType.LENGTH_PREFIXED:
             int len = _decodeLength();