Fix answer file for concurrent_drop_truncate_tablespace

Author: baobao0206

src/test/isolation2/expected/concurrent_drop_truncate_tablespace.out

@@ -131,4 +131,4 @@ SELECT gp_inject_fault('drop_tablespace_after_acquire_lock', 'reset', dbid) FROM
 DROP
 -- fail
 2<:  <... completed>
-ERROR:  could not create directory "pg_tblspc/33175/GPDB_1_302501601/32799": No such file or directory
+ERROR:  tablespace "concurrent_tblspace" does not exist  (seg0 127.0.1.1:7002 pid=1865353)