pgsql: Fix enum value visibility for data_checksums

Fix enum value visibility for data_checksums

When the data_checksums GUC was changed into an enum the enum values
were all incorrectly marked as hidden, which made pg_settings report
an empty array. Fix by setting all as visible as they should be.

Found by Noah using AI assisted review with GPT. Backpatch to v19
where the GUC was changed in the online checksums feature.

Reported-by: Noah Misch <noah(at)leadboat(dot)com>
Discussion: https://postgr.es/m/E15AC050-C4B5-488D-BB2D-3C7AC9F89EA8@yesql.se
Backpatch-through: 19

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3954d740c48750731d4a17766f3cb7b450856ed1

Modified Files
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src/backend/utils/misc/guc_tables.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)