pgsql: Fix publication syntax error message

Fix publication syntax error message

There was some odd wording in corner-case gram.y error messages "some
error ... at or near", which appears to have been modeled after "syntax
error" messages. However, they don't work that way, and they're just
wrong. They're also uncovered by tests. Remove the trailing words,
and also add tests.

They were introduced with 5a2832465fd8; backpatch to 15.

Author: Álvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/8e1d68c8f8eae96334db2f6633d2a61bcfb22f9a

Modified Files
--------------
src/backend/parser/gram.y | 4 ++--
src/test/regress/expected/publication.out | 9 +++++++++
src/test/regress/sql/publication.sql | 4 ++++
3 files changed, 15 insertions(+), 2 deletions(-)