pgsql: In docs, rename "backwards compatibility" to "backward compatibi

In docs, rename "backwards compatibility" to "backward compatibility"
for consistency.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/7a8f43968add3c69b79c49ef236d945e643dcb1e

Modified Files
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doc/src/sgml/array.sgml | 2 +-
doc/src/sgml/config.sgml | 2 +-
doc/src/sgml/func.sgml | 2 +-
doc/src/sgml/libpq.sgml | 4 ++--
doc/src/sgml/lobj.sgml | 2 +-
doc/src/sgml/plperl.sgml | 2 +-
doc/src/sgml/user-manag.sgml | 2 +-
doc/src/sgml/xfunc.sgml | 4 ++--
8 files changed, 10 insertions(+), 10 deletions(-)