ci(ubi-rust-builder): Disable provenance generation

This fixes the image build failures occurring since the last couple
of days. The issue itself is caused by provenance generation, which
produces an image index manifest instead of an image manifest as
before. This then causes the `docker manifest create` command to
fail, because it cannot create index manifests out of other index
manifests, only normal image manifests.

It seems like that a newer Docker version enabled provenance
generation by default. This GHA workflow does NOT pin the exact
docker (and builder) version we use, which seems like the reason
why this issue started popping up without any changes to the
workflow or the Dockerfile for these images. Going forward, we
should pin the exact Docker version we want to use. This will
be done in a separate PR.

For now we chose to disable provenance entirely even though we
want to use it in general. However, we decided to deal with this
once we start to actively work on provenance across our platform.

Author: Techassi

.github/workflows/ubi-rust-builder.yml

@@ -50,6 +50,7 @@ jobs:
           file: ./${{ matrix.ubi-version }}-rust-builder/Dockerfile
           push: true
           tags: oci.stackable.tech/sdp/${{ matrix.ubi-version }}-rust-builder:${{ env.TAG }}
+          provenance: false
       - name: Sign the published builder image
         shell: bash
         env: