Fix comment in fe-connect.c about PQping and pg_ctl

Since f13ea95, pg_ctl does not use PQping(), but one comment did not
get the call.

Author: Euler Taveira
Discussion: https://postgr.es/m/4b1deb4a-2771-416d-9710-ccd2fa66f058@www.fastmail.com

Author: michaelpq

src/interfaces/libpq/fe-connect.c

@@ -3919,8 +3919,7 @@ internal_ping(PGconn *conn)
 		return PQPING_NO_RESPONSE;
 
 	/*
-	 * Report PQPING_REJECT if server says it's not accepting connections. (We
-	 * distinguish this case mainly for the convenience of pg_ctl.)
+	 * Report PQPING_REJECT if server says it's not accepting connections.
 	 */
 	if (strcmp(conn->last_sqlstate, ERRCODE_CANNOT_CONNECT_NOW) == 0)
 		return PQPING_REJECT;