pgsql: doc: Fix documentation of local_preload_libraries

doc: Fix documentation of local_preload_libraries

The documentation used to suggest setting this parameter with ALTER ROLE
SET, but that never worked, so replace it with a working suggestion.

Reported-by: Kyotaro Horiguchi <horiguchi.kyotaro@lab.ntt.co.jp>

Branch
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REL9_2_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/c5d11ebd5ac9e5501d0597fb083ced4bb87a1af2

Modified Files
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doc/src/sgml/config.sgml |    4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)