The upgrade tool is assuming that a type of "list" means list(string) and
a type of "map" means map(string), because that was what we documented
those as meaning.
In practice, Terraform 0.11 was lacking some validation which allowed
more complex nested structures in some cases even though they were pretty
inconvenient to use due to other language limitations.
The upgrade tool doesn't have enough context to make a reliable decision
on this, so instead we'll rely on the upgrade guide for this. We don't
need a TF-UPGRADE-TODO comment in this case because we reserve those for
things where a subsequent operation might cause the configuration to be
misinterpred, rather than just causing an error. Instead, we'll show an
example of the comment in the upgrade guide so the reader can easily
match it, and give some advice in the guide on how to address it.
32d19b9574