pgsql: Fix slot names in the standby slot removal check

Fix slot names in the standby slot removal check

The DROP DATABASE test in 035_standby_logical_decoding.pl created
slots with the prefix "drop_db_" but checked for their removal using
"drop_db". Sined names never existed, the checks passed
even if the actual slots remained.

Fix this by using the correct prefix when checking for slot removal.

Backpatch to v16, where this testce the check was introduced.

Author: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Reviewed-by: Hayato Kuroda <kuroda(dot)hayato(at)fujitsu(dot)com>
Discussion: https://postgr.es/m/CAHGQGwEnuLZnFRF5CzK47n_hXT-iCXnzirxG2v_V-=QNMLkpEA@mail.gmail.com
Backpatch-through: 16

Branch
------
REL_17_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/4ec789e1aa5006ac7c66f9e06fb3495f32459301

Modified Files
--------------
src/test/recovery/t/035_standby_logical_decoding.pl | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)