pgsql: Fix typo in test_oat_hooks README

Fix typo in test_oat_hooks README

Discussion: /messages/by-id/3F066AFE-19F9-4DF5-A498-B09643857A39@yesql.se

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/df64c24a31e110327135a8590c4500887e4773ae

Modified Files
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src/test/modules/test_oat_hooks/README | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)