pgsql: Doc: clean up documentation about text search datatype limits.

Doc: clean up documentation about text search datatype limits.

textsearch.sgml neglected to mention that the MAXSTRPOS total-length
limit applies to tsquery as well as tsvector. It also claims that
there is a 32K limit on the total number of nodes in a tsquery, which
is wrong. (I suspect that QueryOperator.left may once have been
int16, which would give rise to such a limit. But it's uint32 now,
so you'd hit the 1GB varlena limit well before overflowing that.)

While at it, re-order the bullet points into an order that makes
more sense, to me anyway.

Reported-by: Claude Code (via Noah Misch)
Author: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Reviewed-by: Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com>
Discussion: https://postgr.es/m/455079.1786897319@sss.pgh.pa.us
Backpatch-through: 14

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/38e933fafac4db530817571570ef4f550529ffe1

Modified Files
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doc/src/sgml/textsearch.sgml | 21 ++++++++-------------
1 file changed, 8 insertions(+), 13 deletions(-)