Remove the unused field or_connection_t.is_connection_with_client

To discover if a connection is from a tor client, use:
channel_is_client(TLS_CHAN_TO_BASE(or_connection_t.chan))

Part of 21406.

src/or/or.h

@@ -1543,10 +1543,6 @@ typedef struct or_connection_t {
    * NETINFO cell listed the address we're connected to as recognized. */
   unsigned int is_canonical:1;
 
-  /** True iff we have decided that the other end of this connection
-   * is a client.  Connections with this flag set should never be used
-   * to satisfy an EXTEND request.  */
-  unsigned int is_connection_with_client:1;
   /** True iff this is an outgoing connection. */
   unsigned int is_outgoing:1;
   unsigned int proxy_type:2; /**< One of PROXY_NONE...PROXY_SOCKS5 */