SwissSchema should work with any minor/patch Ecto version over 3.x

[joeljuca]

Today, SwissSchema is pinned to work with Ecto versions matching "~> 3.10". However, SwissSchema should be able to work with any Ecto version over the major 3.x.

It would also be good to check if mix.lock reflects the project production deps (aka: prune any dev/test deps from it).