pgsql: Remove a couple of obsolete statements about how many buffers you

Log Message:
-----------
Remove a couple of obsolete statements about how many buffers you can
fit into a 512K shared memory segment.

Modified Files:
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pgsql/doc/src/sgml:
runtime.sgml (r1.351 -> r1.352)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/runtime.sgml.diff?r1=1.351&r2=1.352)