pgsql: Fix accidentally casting away const

Fix accidentally casting away const

Recently introduced in commit b15c1513984.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/75a5914d005b5b65090567eb08343b6a962c89cf

Modified Files
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src/bin/pg_waldump/archive_waldump.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)