Update docker/login-action action to v4 (#173)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [docker/login-action](https://redirect.github.com/docker/login-action)
| action | major | `v3` → `v4` |

---

### Release Notes

<details>
<summary>docker/login-action (docker/login-action)</summary>

###
[`v4`](https://redirect.github.com/docker/login-action/compare/v3...v4)

[Compare
Source](https://redirect.github.com/docker/login-action/compare/v3...v4)

</details>

---

### Configuration

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

🚦 **Automerge**: Enabled.

♻ **Rebasing**: Whenever PR is behind base branch, 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/platform-mesh/resource-broker).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0My40OC4xIiwidXBkYXRlZEluVmVyIjoiNDMuNDguMSIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOltdfQ==-->

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

Author: renovate[bot]

.github/workflows/ci.yml

@@ -68,7 +68,7 @@ jobs:
       - uses: docker/setup-qemu-action@c7c53464625b32c7a7e944ae62b3e17d2b600130 # v3
       - uses: docker/setup-buildx-action@8d2750c68a42422c14e847fe6c8ac0403b4cbd6f # v3
 
-      - uses: docker/login-action@c94ce9fb468520275223c153574b00df6fe4bcc9 # v3
+      - uses: docker/login-action@b45d80f862d83dbcd57f89517bcf500b2ab88fb2 # v4
         with:
           registry: ghcr.io
           username: ${{ github.actor }}