Thread: pgsql: Remove the old advice to keep from_collapse_limit less than

Log Message:
-----------
Remove the old advice to keep from_collapse_limit less than geqo_threshold,
instead just pointing out that a larger value may trigger use of GEQO.
Per Robert Haas.

In passing, do a bit of wordsmithing on the Genetic Query Optimizer section.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        config.sgml (r1.216 -> r1.217)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/config.sgml?r1=1.216&r2=1.217)