Investigate why gosec warns of packages in migration-tool

[Harkishen-Singh]

In https://github.com/timescale/promscale/pull/1286, we separated the migration-tool files under migration-tool which had its own mod file. However, this caused gosec to warn about imports, which looked like false positives to me. We should investigate why gosec warned about the imports. https://github.com/timescale/promscale/pull/1286#discussion_r859272087