[release] Update parent after release xwiki-platform-8.1-milestone-2
[release] Update parent after release xwiki-platform-8.1-milestone-2

xwiki/xwiki-platform,pbondoer/xwiki-platform,xwiki/xwiki-platform,xwiki/xwiki-platform,pbondoer/xwiki-platform,pbondoer/xwiki-platform,xwiki/xwiki-platform,xwiki/xwiki-platform,pbondoer/xwiki-platform,pbondoer/xwiki-platform