Update SCE <-> Seurat faq section

[sjspielman]

From this comment

Really, this section probably needs revision: I'm not sure we need to do SCE->Seurat conversion as manually as we do here, as conversion code seems to have improved and may well handle ADTs more automatically. This is worth testing for a future revision.

Relevant section:

scpca-docs/docs/faq.md

Line 99 in 138525c

## What if I want to use Seurat instead of Bioconductor?