Missing Linux base image for Unity 6000.2.0f1

**Description:**
The Linux base Docker image for Unity version `6000.2.0f1` (`unityci/editor:6000.2.0f1-base-3`) is missing on Docker Hub. Attempting to pull it results in `manifest unknown`, while the Windows variant (`unityci/editor:windows-6000.2.0f1-base-3`) is available.

**Steps to Reproduce:**

```bash
docker pull unityci/editor:6000.2.0f1-base-3 # fails
docker pull unityci/editor:windows-6000.2.0f1-base-3 # succeeds
```

**Expected Behavior:**
Both Linux and Windows base images should be built and published for version `6000.2.0f1`.

**Notes:**

* The versioning-backend correctly scheduled this build (see https://github.com/game-ci/versioning-backend/issues/66).
* This suggests the issue is in the **unity-ci/docker workflows**, where the Linux build may have failed or been skipped.