pgsql: Doc: remove some annoying zero-width spaces.

Doc: remove some annoying zero-width spaces.

To avoid warnings and lines that extend beyond the right page
margin in the PDF documentation, we have zero-width spaces in
the source at strategic places. They are not visible to the
naked eye, but allow FOP to break the lines in sane places.

However, some of these zero-width spaces were in the middle of
text that people might copy and paste from the HTML documentation,
which leads to mysterious syntax errors.

Scanning the documentation for &zwsp; identified four places
that this patch improves:

- an ISO 8601 interval literal didn't actually need a line break
in either the US letter or A4 format, so simply remove that
zero-width space.

- three v18-era examples for uuid_extract_timestamp() and
uuid_extract_version() had zero-width spaces in the middle of UUID
literals. Instead, add regular spaces around the "::" cast symbols,
allowing FOP to break the lines there. This solution isn't
invisible in the HTML output, but it doesn't look bad.

Reported-by: Y. Saburov <y(dot)saburov(at)gmail(dot)com>
Author: Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>
Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Discussion: https://postgr.es/m/179143326813.1061054.14714458907175925072@wrigleys.postgresql.org
Backpatch-through: 18

Branch
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REL_19_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/ef43664e9271538c3f8e9000fd2360de13adec51

Modified Files
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doc/src/sgml/datatype.sgml | 2 +-
doc/src/sgml/func/func-uuid.sgml | 6 +++---
2 files changed, 4 insertions(+), 4 deletions(-)