Adapt to netty5 HttpCookiePair API changes (#23)

Motivation:

We need to adapt to the following netty5 PR, which introduces an API change regarding HttpCookiePair:

netty/netty#13516

Modifications:

the HttpUploadServerHandler in the example needs to be updated in order to parse the request Cookie header using `cookie.encodedCookie()` instead of `cookie.encoded()`

Results:

the codec-multipart project can now be built using latest netty 5.0.0.Alpha6-SNAPSHOT

examples/src/main/java/io/netty/contrib/handler/codec/example/http/multipart/HttpUploadServerHandler.java

@@ -115,7 +115,7 @@ public void messageReceived(ChannelHandlerContext ctx, HttpObject msg) throws Ex
 
             // new getMethod
             for (HttpCookiePair cookie : request.headers().getCookies()) {
-                responseContent.append("COOKIE: " + cookie.encoded() + "\r\n");
+                responseContent.append("COOKIE: " + cookie.encodedCookie() + "\r\n");
             }
 
             responseContent.append("\r\n\r\n");