remove the test for MDEV-16962

after b9d64989 the test for MDEV-16962 is not suitable anymore
(and probably the bug is not reproducible).

mysql-test/suite/gcol/t/innodb_virtual_debug_purge.test

@@ -374,51 +374,4 @@ DROP TABLE t1;
 SET debug_sync= reset;
 set global debug_dbug= @old_dbug;
 
-
---echo # MDEV-16962 Assertion '!error || !ot_ctx.can_recover_from_failed_open()'
---echo # failed in open_purge_table upon concurrent ALTER and FLUSH
-
-CREATE TABLE t1 (
-  pk SERIAL,
-  c VARCHAR(128),
-  d DATE,
-  vd DATE AS (d) VIRTUAL,
-  PRIMARY KEY(pk),
-  KEY(vd,c)
-) ENGINE=InnoDB;
-INSERT IGNORE INTO t1 (pk,c) VALUES (1,'foo');
-
---send
-set debug_sync="now WAIT_FOR purge";
---connect (con1,localhost,root,,test)
-# Will break innodb purge thread inside open_purge_table after mdl
-# acquired, but before tdc->flushed check
-SET GLOBAL innodb_debug_sync="after_open_table_mdl_shared SIGNAL purge WAIT_FOR flush";
-
-# Workaround to pass trx_undo_roll_ptr_is_insert() in 10.2
-SET global debug_dbug="d,ib_purge_virtual_index_callback";
-
-REPLACE INTO t1 (pk,c) VALUES (1,'bar');
-
---connection default
-# wait for MDL acquired by purge
---reap
-# MDL_SHARED will be acquired, but will hang before MDL upgrade started.
-SET debug_sync="alter_table_before_rename_result_table WAIT_FOR flush";
---send
-ALTER TABLE t1 ADD FULLTEXT KEY(c), ALGORITHM=COPY;
---connection con1
-# Will hang after tdc->flushed is set, but before emptying tdc cache.
-SET debug_sync="after_flush_unlock SIGNAL flush ";
-FLUSH TABLES;
-
-# Cleanup
---disconnect con1
---connection default
---reap
---source ../../innodb/include/wait_all_purged.inc
-DROP TABLE t1;
-SET debug_sync= reset;
-SET global debug_dbug=@old_dbug;
-
 SET GLOBAL innodb_purge_rseg_truncate_frequency = @saved_frequency;