ci: no Blacksmith builder's config to ignore

The release no longer runs useblacksmith/setup-docker-builder, so nothing writes buildkitd.toml
into the checkout: its ignore lines and the test that held them guard a step that is gone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: aledbf

.gitignore

@@ -8,8 +8,3 @@ coverage.xml
 .claude/
 .task/
 
-# BuildKit daemon configs that useblacksmith/setup-docker-builder writes into the
-# job's working directory (the repo checkout) in the release workflow. Left
-# untracked they make the tree dirty and GoReleaser refuses to release.
-/buildkitd.toml
-/docker-container-buildkitd.toml