Description of problem:

Currently the project-velero/kopia is being used in the oadp-operator. This is fine as our downstream version does not include any additional patches or changes. 

We should switch to use our own fork migtools/kopia even if it's not diverged from the upstream.

Steps to Reproduce:
1. checkout source code of an oadp-operator
2. confirm the go.mod contains line:
    replace github.com/kopia/kopia => github.com/project-velero/kopia [...]

Actual results:
kopia/kopia is being replaced by project-velero/kopia

Expected results:
kopia/kopia should be replaced by migtools/kopia