pgbench: Remove dead code

doConnect() never returns connections in state CONNECTION_BAD, so
checking for that is pointless.  Remove the code that does.

This code has been dead since ba708ea3, 20 years ago.

Discussion: https://postgr.es/m/20210126195224.GA20361@alvherre.pgsqlReviewed-by: Tom Lane <tgl@sss.pgh.pa.us>

src/bin/pgbench/pgbench.c

@@ -6040,13 +6040,6 @@ main(int argc, char **argv)
 	if (con == NULL)
 		exit(1);
 
-	if (PQstatus(con) == CONNECTION_BAD)
-	{
-		pg_log_fatal("connection to database \"%s\" failed: %s",
-					 dbName, PQerrorMessage(con));
-		exit(1);
-	}
-
 	if (internal_script_used)
 		GetTableInfo(con, scale_given);