build: Use bib

- It's not worth shipping around a distinct build container;
  bootc-image-builder already has all the dependencies we need
  since https://github.com/osbuild/bootc-image-builder/pull/176/commits/44d15acded8641499ea6b4c5d2acceb1bd9694b2
- I'd like to add a more first-class mechanism in bib to build
  base images

.github/workflows/build-image.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
 
     container:
-      image: quay.io/centos-bootc/builder:latest
+      image: quay.io/centos-bootc/bootc-image-builder:latest
       options: --privileged
 
     strategy: