pgsql: Fix a handful of typos in the release notes introduced by Bruce's

Log Message:
-----------
Fix a handful of typos in the release notes introduced by Bruce's recent
commit. Per Gavin Sherry.

Modified Files:
--------------
pgsql/doc/src/sgml:
release.sgml (r1.307 -> r1.308)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/release.sgml.diff?r1=1.307&r2=1.308)