pgsql: Mention REINDEX CONCURRENTLY in documentation about indexmainte

Mention REINDEX CONCURRENTLY in documentation about index maintenance

The documentation includes a section about index maintenance and
reindexing, mentioning a set of steps based on CREATE INDEX CONCURRENTLY
and ALTER TABLE (for constraint dependencies) to emulate REINDEX
CONCURRENTLY.  Now that REINDEX CONCURRENTLY is supported, let's just
directly mention it instead.

Reported-by: Peter Geoghegan
Author: Michael Paquier
Reviewed-by: Peter Eisentraut, Tom Lane
Discussion: https://postgr.es/m/CAH2-WzmEL168t6w29aKrKXtpq9-apcmp0HC7K-fKt6ZgLXV6Dg@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a967878414f906a7f88842424c667a5ac31b9625

Modified Files
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doc/src/sgml/maintenance.sgml | 17 ++++-------------
1 file changed, 4 insertions(+), 13 deletions(-)