I experienced the same issue.
Similar to @Ivor, resetting the dependencies helped me.
rm mix.lock; rm -rf _build; rm -rf deps; mix deps.get
Before: Parantheses added by mix format, e.g. to ecto field macro.
After: Parantheses no longer added.
I did not test if all the steps were necessary, or if a single one of them might have helped.
