gitlab: Change package name to gitlab.wikimedia.org/repos/releng/blubber
We're migrating Blubber to the WMF GitLab instance. For a go project, this means all package base names need to change for use with go tools.
Replaced all references to gerrit.wikimedia.org/r/blubber with
references to gitlab.wikimedia.org/repos/releng/blubber and ran go mod tidy
.
There is documentation around contributing that still needs updating, but that can be done in a follow up.
Bug: T321225 Change-Id: I6388cbefd796963bf8bcf6e5b7ef84b0142f1dd6