minor doc issues.

hi

https://www.postgresql.org/docs/current/datatype-json.html
Table 8.23. JSON Primitive Types and Corresponding PostgreSQL Types

"SQL NULL is a different concept"
can we change to
"Only accept lowercase null. SQL NULL is a different concept"
I saw people ask similar questions on stackoverflow. maybe worth mentioning.

-----
https://www.postgresql.org/docs/16/view-pg-backend-memory-contexts.html
Table 54.4. pg_backend_memory_contexts Columns
should be
Table 54.4. pg_backend_memory_contexts View.