Use Bugzilla instead of invent for Bug reporting address
KDE products don't use invent.gitlab.org for reporting bugs, for the reasons outlined in https://community.kde.org/Get_Involved/Issue_Reporting/Why_not_GitLab_Issues.
This commit changes the bug reporting address listed in the AppStream metadata so that it points to the appropriate Bugzilla component.
Fixes #83 (closed)