"splice is not defined" fix on MEP.remove() [follow-up from #779 and #788]

#788 tried to fix part of what #779 did, but didn't acknowledge that
`mejs.players` is no longer an array, being an object now (a change
introduced by #779). As such, remove() now throws a "splice is not
defined" error at that point.

This fix replaces the line added by #788 with #779's equivalent, but
preserves (and rectifies) the comment above.