pgsql: Fix typo: < one column or expression indexes, perhaps using

Log Message:
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Fix typo:

< one column or expression indexes, perhaps using per=index statistics

one column or expression indexes, perhaps using per-index statistics

Modified Files:
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pgsql/doc:
TODO (r1.1382 -> r1.1383)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1382&amp;r2=1.1383)