MDEV-21563 FTS thread aborts during shutdown

- Add warning suppression in misc_debug2 test.

mysql-test/suite/innodb_fts/r/misc_debug2.result

 call mtr.add_suppression("InnoDB: Table '.*' tablespace is set as discarded.");
+call mtr.add_suppression("InnoDB: Tablespace for table .* is set as discarded.");
 CREATE TABLE mdev21563(f1 VARCHAR(100), FULLTEXT idx(f1))ENGINE=InnoDB;
 set debug_dbug="+d,fts_instrument_sync_request";
 INSERT INTO mdev21563 VALUES('This is a test');

mysql-test/suite/innodb_fts/t/misc_debug2.test

@@ -2,6 +2,7 @@
 --source include/have_debug.inc
 --source include/not_embedded.inc
 call mtr.add_suppression("InnoDB: Table '.*' tablespace is set as discarded.");
+call mtr.add_suppression("InnoDB: Tablespace for table .* is set as discarded.");
 
 CREATE TABLE mdev21563(f1 VARCHAR(100), FULLTEXT idx(f1))ENGINE=InnoDB;
 set debug_dbug="+d,fts_instrument_sync_request";