pgsql: doc: \copy can get data values \. and end-of-input confused

doc: \copy can get data values \. and end-of-input confused

Reported-by: Svante Richter

Discussion: /messages/by-id/fcd57e4-8f23-4c3e-a5db-2571d09208e2@beta.fastmail.com

Backpatch-through: 11

Branch
------
REL_14_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/d1d80ef0115d5c7a079136403528a485c3c48586

Modified Files
--------------
doc/src/sgml/ref/psql-ref.sgml | 4 ++++
src/bin/psql/copy.c | 1 +
2 files changed, 5 insertions(+)