Cleanup: Remove a test hack

Merge commit 2b6f8044 introduced
the debug injection point dict_sys_mutex_avoid to make the test
innodb.instant_alter_crash work even after the MDEV-23991 fix
(commit afc9d00c).

Thanks to DDL being atomic and crash-safe in MariaDB 10.6
(mainly thanks to commit 7762ee5d)
we do not actually need this hack anymore.

mysql-test/suite/innodb/r/instant_alter_crash.result

@@ -40,7 +40,6 @@ ALTER TABLE t2 DROP COLUMN c3, ADD COLUMN c5 TEXT DEFAULT 'naturam abhorrere';
 connection default;
 SET DEBUG_SYNC='now WAIT_FOR ddl';
 SET GLOBAL innodb_flush_log_at_trx_commit=1;
-SET debug_dbug='+d,dict_sys_mutex_avoid';
 UPDATE t1 SET c2=c2+1;
 # Kill the server
 disconnect ddl;
@@ -69,7 +68,6 @@ ALTER TABLE t2 ADD COLUMN (c4 TEXT NOT NULL DEFAULT ' et malorum');
 connection default;
 SET DEBUG_SYNC='now WAIT_FOR ddl';
 SET GLOBAL innodb_flush_log_at_trx_commit=1;
-SET debug_dbug='+d,dict_sys_mutex_avoid';
 DELETE FROM t1;
 # Kill the server
 disconnect ddl;
@@ -149,7 +147,6 @@ ALTER TABLE t3 ADD COLUMN c3 TEXT NOT NULL DEFAULT 'sic transit gloria mundi';
 connection default;
 SET DEBUG_SYNC='now WAIT_FOR ddl';
 SET GLOBAL innodb_flush_log_at_trx_commit=1;
-SET debug_dbug='+d,dict_sys_mutex_avoid';
 INSERT INTO t1 VALUES(0,0);
 # Kill the server
 disconnect ddl;

mysql-test/suite/innodb/t/instant_alter_crash.test

@@ -55,7 +55,6 @@ ALTER TABLE t2 DROP COLUMN c3, ADD COLUMN c5 TEXT DEFAULT 'naturam abhorrere';
 connection default;
 SET DEBUG_SYNC='now WAIT_FOR ddl';
 SET GLOBAL innodb_flush_log_at_trx_commit=1;
-SET debug_dbug='+d,dict_sys_mutex_avoid';
 UPDATE t1 SET c2=c2+1;
 
 --source include/kill_mysqld.inc
@@ -84,7 +83,6 @@ ALTER TABLE t2 ADD COLUMN (c4 TEXT NOT NULL DEFAULT ' et malorum');
 connection default;
 SET DEBUG_SYNC='now WAIT_FOR ddl';
 SET GLOBAL innodb_flush_log_at_trx_commit=1;
-SET debug_dbug='+d,dict_sys_mutex_avoid';
 DELETE FROM t1;
 
 --source include/kill_mysqld.inc
@@ -191,7 +189,6 @@ ALTER TABLE t3 ADD COLUMN c3 TEXT NOT NULL DEFAULT 'sic transit gloria mundi';
 connection default;
 SET DEBUG_SYNC='now WAIT_FOR ddl';
 SET GLOBAL innodb_flush_log_at_trx_commit=1;
-SET debug_dbug='+d,dict_sys_mutex_avoid';
 INSERT INTO t1 VALUES(0,0);
 
 --source include/kill_mysqld.inc

storage/innobase/handler/ha_innodb.cc

@@ -14374,8 +14374,6 @@ ha_innobase::info_low(
 		stats.update_time = (ulong) ib_table->update_time;
 	}
 
-	DBUG_EXECUTE_IF("dict_sys_mutex_avoid", goto func_exit;);
-
 	dict_stats_init(ib_table);
 
 	if (flag & HA_STATUS_VARIABLE) {