update doc release notes in prep for 2.5.0beta1 release

git-svn-id: http://svn.osgeo.org/postgis/trunk@16631 b70326c6-7e19-0410-871a-916f4a2858ee
1 job for svn-trunk in 19 minutes and 7 seconds
Status Job ID Name Coverage
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passed #79184267
test

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