Remove misleading function comment (bug 5324)

In the distant past, connection_handle_read() could be called when there
are pending bytes in the TLS object during the main loop. The design
since then has been to always read all pending bytes immediately, so
read events only trigger when the socket actually has bytes to read.

Resolves bug 5324.

src/or/connection.c

@@ -2594,10 +2594,6 @@ connection_consider_empty_read_buckets(connection_t *conn)
 #endif
 
 /** Read bytes from conn-\>s and process them.
- *
- * This function gets called from conn_read() in main.c, either
- * when poll() has declared that conn wants to read, or (for OR conns)
- * when there are pending TLS bytes.
  *
  * It calls connection_read_to_buf() to bring in any new bytes,
  * and then calls connection_process_inbuf() to process them.