Removed redundant assignment (#10853)

Motivation:

Found a redundant assignment.

Modification:

Removed the redundant assignment.

Result:

Minor performance improvement.

handler/src/main/java/io/netty/handler/stream/ChunkedNioStream.java

@@ -60,7 +60,6 @@ public class ChunkedNioStream implements ChunkedInput<ByteBuf> {
                     " (expected: a positive integer)");
         }
         this.in = in;
-        offset = 0;
         this.chunkSize = chunkSize;
         byteBuffer = ByteBuffer.allocate(chunkSize);
     }