twoliter: fetch instead of fetch-sdk for builds

[webern]

Issue number:

Fixes #214

Description of changes:

We accidentally removed "fetch" from the Makefile.toml dependency graph when building a variant. This change restores it.

Get fetch back into the dependency graph for build-variant and build-package.

Testing done:

• Before this fix I would get an error during go mod vendor and could see that fetch-vendored was not running.
• After this fix, Bottlerocket builds.

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.