pgsql: Rename log_lock_failure GUC to log_lock_failures for consistency

Rename log_lock_failure GUC to log_lock_failures for consistency.

This commit renames the GUC log_lock_failure to log_lock_failures
to align with the existing similar setting log_lock_waits, which uses
the plural form. This improves naming consistency across related GUCs.

Suggested-by: Peter Eisentraut <peter(at)eisentraut(dot)org>
Author: Fujii Masao <masao(dot)fujii(at)gmail(dot)com
Reviewed-by: Peter Eisentraut <peter(at)eisentraut(dot)org>
Discussion: https://postgr.es/m/7a8198b6-d5b8-4910-b41e-8d3efcbb015d@eisentraut.org

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/73bdcfab35ec0a7eff1a5dd630cbad8e77054547

Modified Files
--------------
doc/src/sgml/config.sgml | 6 +++---
doc/src/sgml/release-18.sgml | 2 +-
src/backend/access/heap/heapam.c | 6 +++---
src/backend/access/heap/heapam_handler.c | 2 +-
src/backend/storage/lmgr/lock.c | 2 +-
src/backend/utils/misc/guc_tables.c | 4 ++--
src/backend/utils/misc/postgresql.conf.sample | 2 +-
src/include/storage/lock.h | 2 +-
8 files changed, 13 insertions(+), 13 deletions(-)