pgsql: Revert "Fix psql's single transaction mode on client-side errors

Revert "Fix psql's single transaction mode on client-side errors with -c/-f switches".

This reverts commits a04ccf6df et al. in the back branches only.
There was some disagreement already over whether to back-patch
157f8739a, on the grounds that it is the sort of behavioral
change that we don't like to back-patch. Furthermore, it now
looks like the logic needs some more work, which we don't have
time for before the upcoming 14.4 release. Revert for now, and
perhaps reconsider later.

Discussion: https://postgr.es/m/17504-76b68018e130415e@postgresql.org

Branch
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REL_10_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/db713aa7fcbe2ad2a5dae7f76c309f70ec424ad7

Modified Files
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doc/src/sgml/ref/psql-ref.sgml | 6 ++----
src/bin/psql/startup.c | 4 +---
2 files changed, 3 insertions(+), 7 deletions(-)