Update release date

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxPython/trunk@76879 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Add a note about prerequisites

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxPython/trunk@76880 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Fix typo

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxPython/trunk@76881 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775