Fix documentation link to issue template

On the Ansible Community page (http://docs.ansible.com/community.html)
in the "I'd like to report a bug" section, the link to the "issue
template" is broken - it links to URL
https://raw2.github.com/ansible/ansible/devel/ISSUE_TEMPLATE.md, which
results in a GitHub 404 (Page not found) error page .

Fix points link to a URL that works.