pgsql: doc: fix typo in release notes - Mailing list pgsql-committers

doc:  fix typo in release notes

Backpatch through 8.4

Per suggestion by Amit Langote

Branch
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REL9_1_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/6defa661e0f69c0a3fa1526b3536fe3f63005bc4

Modified Files
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doc/src/sgml/release-8.4.sgml |    4 ++--
doc/src/sgml/release-9.0.sgml |    4 ++--
doc/src/sgml/release-9.1.sgml |    4 ++--
3 files changed, 6 insertions(+), 6 deletions(-)