Remove dead code

Motivation:

We used to have a double lookup for Connection header, based on case.
But HttpHeaders lookup is case insensitive and I forgot to remove this
code that now performs the lookup twice.

Modification:

Remove dead code

Result:

Dead code removed

client/src/main/java/org/asynchttpclient/netty/handler/WebSocketHandler.java

@@ -87,8 +87,6 @@ public void call() throws Exception {
             boolean validStatus = response.status().equals(SWITCHING_PROTOCOLS);
             boolean validUpgrade = response.headers().get(UPGRADE) != null;
             String connection = response.headers().get(CONNECTION);
-            if (connection == null)
-                connection = response.headers().get(CONNECTION);
             boolean validConnection = HttpHeaderValues.UPGRADE.contentEqualsIgnoreCase(connection);
             boolean statusReceived = handler.onStatusReceived(status) == State.CONTINUE;