Fix sorting key for Total table header

[democat3457]

When clicking the --- Total --- header in the Delta-focused stats table, the table doesn't sort by the completion time.

This is because the sorting key provided when creating the Total header has a different sorting key than the Points header does. Changing the key from "total" to "completion" to match the sorting key of the Points header fixes the sorting.

[jeroenheijmans]

Oh my that's broken indeed! Thanks for the PR, that helps a ton. I do have some personal stuff going on, so not sure when I'll get to releaseing it (the check + merge is easily done soon, but building and releasing the addon in stores is a bit of manual labor at the moment).