Further cleanup for recent JSON-related commits.

Tom Lane <tgl@sss.pgh.pa.us>

Commit: 2497a669effbbdda3e7be573d850b445d1ab6512
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: 2024-04-04T17:21:25Z
Releases: 17.0
Further cleanup for recent JSON-related commits.

Add overlooked .gitignore entries.

Fix test_json_parser/Makefile to use the pgxs.mk clean rule
instead of fighting it.  Suppresses a warning from make,
at least for me.

Files