Update index.adoc link to Fedora Diversity page

Currently the link in the index for the DEI page is: https://docs.fedoraproject.org/en-US/diversity-inclusion/ however, the correct link is: https://docs.fedoraproject.org/en-US/dei/ This results in an error if the link is followed by an Italian example translated page like https://docs.fedoraproject.org/it/diversity-inclusion/ Link fixed.