chore(deps): update actions/attest-build-provenance action to v3 (#38)

Coming soon: The Renovate bot (GitHub App) will be renamed to Mend. PRs
from Renovate will soon appear from 'Mend'. Learn more
[here](https://redirect.github.com/renovatebot/renovate/discussions/37842).

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
|
[actions/attest-build-provenance](https://redirect.github.com/actions/attest-build-provenance)
| action | major | `v2` -> `v3` |

---

### Release Notes

<details>
<summary>actions/attest-build-provenance
(actions/attest-build-provenance)</summary>

###
[`v3`](https://redirect.github.com/actions/attest-build-provenance/compare/v2...v3)

[Compare
Source](https://redirect.github.com/actions/attest-build-provenance/compare/v2...v3)

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined),
Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you
are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the
rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update
again.

---

- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check
this box

---

This PR was generated by [Mend Renovate](https://mend.io/renovate/).
View the [repository job
log](https://developer.mend.io/github/morten-olsen/homelab-operator).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0MS45Ny4xMCIsInVwZGF0ZWRJblZlciI6IjQxLjk3LjEwIiwidGFyZ2V0QnJhbmNoIjoibWFpbiIsImxhYmVscyI6W119-->

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.github/workflows/publish-backup-tag.yml

@@ -58,7 +58,7 @@ jobs:
           labels: ${{ steps.meta.outputs.labels }}
 
       - name: Generate artifact attestation
-        uses: actions/attest-build-provenance@v2
+        uses: actions/attest-build-provenance@v3
         with:
           subject-name: ${{ env.DOCKER_REGISTRY }}/${{ env.IMAGE_NAME}}
           subject-digest: ${{ steps.push.outputs.digest }}

.github/workflows/publish-tag.yml

@@ -58,7 +58,7 @@ jobs:
           labels: ${{ steps.meta.outputs.labels }}
 
       - name: Generate artifact attestation
-        uses: actions/attest-build-provenance@v2
+        uses: actions/attest-build-provenance@v3
         with:
           subject-name: ${{ env.DOCKER_REGISTRY }}/${{ env.IMAGE_NAME}}
           subject-digest: ${{ steps.push.outputs.digest }}