Update wiki.mahara.org releases page

📗 Update wiki.mahara.org releases page

1. Go to the releases page's section 'Current and upcoming releases.'
2. Update the text: "The latest stable version of Mahara is MAJOR_VERSION , released on DATE"
3. Add a new row for the major release. (If you edit the area, there is a template available to copy)
4. Add the release date and release notes for the minor point releases linking to the forum post announcement now that there no longer will be releases in launchpad: https://mahara.org/interaction/forum/topic.php?id=9296)
5. Update the major version where 18 months has passed since its release to be 'unsupported'.