circular dependency check must be version constrained

[gforcada]

Otherwise a new package gets released and it is being used on the circular dependency check 😕

With the following changes it should be fine to get it to work again 🍀

constrain_package_deps = true
deps =
    ...
    -c my-constraints-file.txt

This is even more visible when one is still on Plone 5.2 and tries to configure an internal package 🤚🏾

But as we generalize plone/meta enough to get collective packages to be covered, and for that with multiple python and plone versions support, it will be a must.

[gforcada]

There is already an option to set a constraints.txt but we are missing the constrain_package_deps still