pgsql: Doc: fix examples for pg_input_error_info().

Doc: fix examples for pg_input_error_info().

These were causing "contents ... exceed the available area"
warnings in PDF builds, and also didn't quite follow our markup
conventions for function examples.  To fix the overwidth
problem, reduce the number of fields shown in one example,
and also insert &zwsp; to let the header line be broken in
a reasonable place.

Discussion: https://postgr.es/m/20230324194701.dqkzcdtlcikseo22@awork3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/7023207cfdb6d5863bdcc9c29bff9918846dddc6

Modified Files
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doc/src/sgml/func.sgml | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)