Fix typos and grammar in the code

The large majority of these have been introduced by recent commits done
in the v18 development cycle.

Author: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/9a7763ab-5252-429d-a943-b28941e0e28b@gmail.com

src/interfaces/libpq/fe-cancel.c

@@ -50,7 +50,7 @@ struct pg_cancel
 									 * retransmits */
 
 	/* Pre-constructed cancel request packet starts here */
-	int32		cancel_pkt_len; /* in network-byte-order */
+	int32		cancel_pkt_len; /* in network byte order */
 	char		cancel_req[FLEXIBLE_ARRAY_MEMBER];	/* CancelRequestPacket */
 };