pgsql: Fix argument handling in pg_indexam_progress_phasename()

Fix argument handling in pg_indexam_progress_phasename()

The function is declared in pg_proc.dat a bigint as its second input
argument, but the function's code used PG_GETARG_INT32().

This is an issue in 32-bit architectures in stable branches (up to v18)
where bigint is still passed by reference, reporting bogus numbers.
Since 2a600a93c7b (v19 and HEAD), this is less of a problem as Datums
became 8-byte wide everywhere.

Oversight in ab0dfc961b6.

Author: Markos Fountoulakis <markos(at)planetscale(dot)com>
Reviewed-by: Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com>
Discussion: https://postgr.es/m/e791bbb7-af3a-4a91-a5bb-c744e5c3ef54@planetscale.com
Backpatch-through: 14

Branch
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REL_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/6f126b32893354561b271f783531c3d6a2ebce0e

Modified Files
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src/backend/utils/adt/amutils.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)