user v0.3.0

What's Changed

• remove userns package that was added in v0.2.0
• downgrade minimum go version to v1.17
• retract v0.2.0

Breaking changes

This release removes the userns package, which was added in v0.2.0, and
now retracted. Commit 86870e7 integrated the userns package into the
github.com/moby/sys/user module, which was included in the v0.2.0 version
of the module.

After further discussion with maintainers, this was not a good choice,
as the package has no direct relation with "user" operations (other than
their name).

For that reason, the userns package was move to its own module and can
now be found in the github.com/moby/sys/userns module.

This release retracts the previous (v0.2.0) release and removes the userns
package, effectively reverting the module to v0.1.0.

Full Changelog: user/v0.2.0...user/v0.3.0