Revert "dependencies: Do not hard fail when a commit cannot be resolved"

Created by: bobheadxi

Reverts sourcegraph/sourcegraph#35679

I just had this flake 3x 4x on a single build, and I've seen this across several PRs today:

• https://buildkite.com/sourcegraph/sourcegraph/builds/148610#38bc5b67-295c-4198-b346-8c44183e59fb
• https://buildkite.com/sourcegraph/sourcegraph/builds/148629#57c98ffd-c19b-4fe9-8656-515ad92b9bef
• branch cut failed as well on this flake: https://buildkite.com/sourcegraph/sourcegraph/builds/148645#726f3d74-9e19-4d64-bdfd-4f0a76308169

Test plan: this build passes