pgsql: Assorted minor cleanups in the test_json_parser module

Assorted minor cleanups in the test_json_parser module

Per gripes from Michael Paquier

Discussion: /messages/by-id/ZhTQ6_w1vwOhqTQI@paquier.xyz

Along the way, also clean up a handful of typos in 3311ea86ed and
ea7b4e9a2a, found by Alexander Lakhin, and a couple of stylistic
snafus noted by Daniel Westermann and Daniel Gustafsson.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/42fa4b660143b66bea1fb90793ec90054e170c93

Modified Files
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src/backend/backup/basebackup_incremental.c | 6 ++---
src/common/jsonapi.c | 6 ++---
src/common/parse_manifest.c | 2 +-
src/test/modules/test_json_parser/README | 19 +++++++--------
.../test_json_parser_incremental.c | 28 ++++++++++++++++------
.../test_json_parser/test_json_parser_perf.c | 11 +++++----
6 files changed, 43 insertions(+), 29 deletions(-)