Remove some code related to 7.3 and older servers from tools of src/bin/

This code was broken as of 582edc36, and is most likely not used anymore.
Note that pg_dump supports servers down to 8.0, and psql has code to
support servers down to 7.4.

Author: Julien Rouhaud
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/CAOBaU_Y5y=zo3+2gf+2NJC1pvMYPcbRXoQaPXx=U7+C8Qh4CzQ@mail.gmail.com

src/bin/scripts/common.c

@@ -136,7 +136,6 @@ connectDatabase(const char *dbname, const char *pghost,
 		exit(1);
 	}
 
-	if (PQserverVersion(conn) >= 70300)
 	PQclear(executeQuery(conn, ALWAYS_SECURE_SEARCH_PATH_SQL,
 						 progname, echo));
 
@@ -302,13 +301,6 @@ appendQualifiedRelation(PQExpBuffer buf, const char *spec,
 	PGresult   *res;
 	int			ntups;
 
-	/* Before 7.3, the concept of qualifying a name did not exist. */
-	if (PQserverVersion(conn) < 70300)
-	{
-		appendPQExpBufferStr(&sql, spec);
-		return;
-	}
-
 	split_table_columns_spec(spec, PQclientEncoding(conn), &table, &columns);
 
 	/*