pgsql: Fix typo: < Currently indexes do not have enough tuple tuple

Log Message:
-----------
Fix typo:

< Currently indexes do not have enough tuple tuple visibility
< information to allow data to be pulled from the index without
< also accessing the heap. One way to allow this is to set a bit
< to index tuples to indicate if a tuple is currently visible to
< all transactions when the first valid heap lookup happens. This
< bit would have to be cleared when a heap tuple is expired.

Currently indexes do not have enough tuple visibility information
to allow data to be pulled from the index without also accessing
the heap. One way to allow this is to set a bit to index tuples
to indicate if a tuple is currently visible to all transactions
when the first valid heap lookup happens. This bit would have to
be cleared when a heap tuple is expired.

Modified Files:
--------------
pgsql/doc:
TODO (r1.1503 -> r1.1504)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1503&amp;r2=1.1504)
pgsql/doc/src/FAQ:
TODO.html (r1.10 -> r1.11)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.10&amp;r2=1.11)