pgsql: Doc: adjust documentation related to index support functions.

Doc: adjust documentation related to index support functions.

Commit 15cb2bd27 neglected to make the running text match the
tables, leaving the reader with the strong impression that
we cannot count.  Also, don't drop an unrelated para between
a table and the para describing it.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a273dcc6fd34c8b6aa290fafa45e516ccd8d907d

Modified Files
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doc/src/sgml/xindex.sgml | 32 ++++++++++++++++----------------
1 file changed, 16 insertions(+), 16 deletions(-)