Fix query checking consistency of table amhandlers in opr_sanity.sql

Fix query checking consistency of table amhandlers in opr_sanity.sql

As written, the query checked for an access method of type 's', which is
not an AM type supported in the core code.

Error introduced by 8586bf7ed888.  As this query is not checking what it
should, backpatch all the way down.

Reviewed-by: Aleksander Alekseev
Discussion: https://postgr.es/m/ZVxJkAJrKbfHETiy@paquier.xyz
Backpatch-through: 12