pgsql: Fix some errhint and errdetail strings missing a period

Fix some errhint and errdetail strings missing a period

As per the error message style guide of the documentation, those should
be full sentences.

Author: Daniel Gustafsson
Reviewed-by: Michael Paquier, Álvaro Herrera
Discussion: https://1E8D49B4-16BC-4420-B4ED-58501D9E076B@yesql.se

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/730422afcdb6784bbe20efc65de72156d470b0c4

Modified Files
--------------
contrib/amcheck/verify_nbtree.c        |  2 +-
src/backend/commands/tablecmds.c       |  2 +-
src/backend/utils/adt/jsonfuncs.c      |  4 ++--
src/backend/utils/misc/guc.c           |  6 +++---
src/pl/plpgsql/src/pl_exec.c           |  2 +-
src/test/regress/expected/json.out     |  6 +++---
src/test/regress/expected/jsonb.out    |  6 +++---
src/test/regress/expected/plpgsql.out  | 16 ++++++++--------
src/test/regress/expected/triggers.out |  2 +-
9 files changed, 23 insertions(+), 23 deletions(-)