[cleanup][proxy] ProxyConnection should not call super.exceptionCaught (#19990)

### Motivation

While debugging an issue, I noticed that we call `super.exceptionCaught(ctx, cause);` in the `ProxyConnection` class. This leads to the following log line:

> An exceptionCaught() event was fired, and it reached at the tail of the pipeline. It usually means the last handler in the pipeline did not handle the exception. io.netty.channel.unix.Errors$NativeIoException: recvAddress(..) failed: Connection reset by peer

Because we always handle exceptions, there is no need to forward them to the next handler.

### Modifications

* Remove a single method call

### Verifying this change

This is a trivial change. Note that we do not call the super method in any other handler implementations in the project.

### Documentation

- [x] `doc-not-needed` <!-- Your PR changes do not impact docs -->

### Matching PR in forked repository

PR in forked repository: skipping PR for this trivial change

Author: michaeljmarshall

pulsar-proxy/src/main/java/org/apache/pulsar/proxy/server/ProxyConnection.java

@@ -208,7 +208,6 @@ public synchronized void channelInactive(ChannelHandlerContext ctx) throws Excep
 
     @Override
     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
-        super.exceptionCaught(ctx, cause);
         LOG.warn("[{}] Got exception {} : Message: {} State: {}", remoteAddress, cause.getClass().getSimpleName(),
                 cause.getMessage(), state,
                 ClientCnx.isKnownException(cause) ? null : cause);