Make innodb_gis.rtree_purge run faster

A locking SELECT from an InnoDB table is very slow especially
in debug builds. Replacing some INSERT...SELECT should not reduce
the test coverage, because the test will still do DELETE
(which will acquire explicit record locks).

mysql-test/suite/innodb_gis/t/rtree_purge.test

 # This test case will test R-tree purge.
 
 --source include/innodb_page_size.inc
-# Valgrind takes too much time on PB2 even in the --big-test runs.
+--source include/have_sequence.inc
 --source include/not_valgrind.inc
 
 SET @saved_frequency = @@GLOBAL.innodb_purge_rseg_truncate_frequency;
@@ -16,9 +16,7 @@ set @p=point(1,1);
 let $n=200;
 while ($n) {
 begin;
-insert into t values(@p,@p),(@p,@p);
-insert into t select @p,@p
-from t a,t b,t c,t d,t e,t f,t g;
+insert into t select @p,@p from seq_1_to_130;
 delete from t;
 commit;
 dec $n;