## Summary
We don't enable E501 by default, but `line-length` is a useful example
for configuration, so we now set `--extend-select` in the tutorial with
a note to that effect.
I've also updated all the outputs to match the latest CLI behavior, and
changed the example from `List` to `Sequence` because `List` now spits
out two diagnostics (one for the import, one for the usage), which IMO
is confusing for beginners.
cdc5e2fb58