nghttpx: Remove unused private field from Connection object

src/shrpx_connection.cc

@@ -61,9 +61,6 @@ Connection::Connection(struct ev_loop *loop, int fd, SSL *ssl,
     : tls{DefaultMemchunks(mcpool), DefaultPeekMemchunks(mcpool)},
       wlimit(loop, &wev, write_limit.rate, write_limit.burst),
       rlimit(loop, &rev, read_limit.rate, read_limit.burst, this),
-      writecb(writecb),
-      readcb(readcb),
-      timeoutcb(timeoutcb),
       loop(loop),
       data(data),
       fd(fd),

src/shrpx_connection.h

@@ -125,9 +125,6 @@ struct Connection {
   ev_timer rt;
   RateLimit wlimit;
   RateLimit rlimit;
-  IOCb writecb;
-  IOCb readcb;
-  TimerCb timeoutcb;
   struct ev_loop *loop;
   void *data;
   int fd;