Use a list in drop_coords instead of a set for older versions of Scipp

[nvaytet]

Older versions of scipp require a list and do not work with a set in drop_coords.
This is to fix the nightly test at lower bounds.

The alternative to this fix would be to bump the min version of scipp in the runtime dependencies of essreduce...

[MridulS]

The alternative to this fix would be to bump the min version of scipp in the runtime dependencies of essreduce...

In my opinion being aggresive in dropping old version is better as we currently have the luxury of not having too many downstream users 😅 and we don't need to maintain these quirks.

[nvaytet]

In my opinion being aggresive in dropping old version is better as we currently have the luxury of not having too many downstream users 😅 and we don't need to maintain these quirks.

Could be, but in this case, it was such a small change in a single place, that I thought it wasn't worth the time trying to dig through all the releases to find the one with the change. Also, it's not that essreduce can't work at all with the older scipp, so I think being lenient with requirements is worth it.