Fix spelling in javadocs and field name.

Motivation:

Fix a spell mistake.

Modifications:

Change 'treshold' to 'threshold'

Result:

The spellchecker warnings of the IDE disappeared.

codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocket08FrameEncoder.java

@@ -82,7 +82,7 @@ public class WebSocket08FrameEncoder extends MessageToMessageEncoder<WebSocketFr
     private static final byte OPCODE_PONG = 0xA;
 
     /**
-     * The size thsreshold for gathering writes. Non-Masked messages bigger than this size will be be sent fragmented as
+     * The size threshold for gathering writes. Non-Masked messages bigger than this size will be be sent fragmented as
      * a header and a content ByteBuf whereas messages smaller than the size will be merged into a single buffer and
      * sent at once.<br>
      * Masked messages will always be sent at once.