feat: 更新Docker CI工作流，修正镜像名称为短链接服务

Author: AptS-1547

.github/workflows/docker-image.yml

@@ -40,7 +40,7 @@ jobs:
       uses: docker/metadata-action@v5
       with:
         images: |
-          e1saps/onebot-github-webhook
+          e1saps/shortlinker
           ghcr.io/${{ github.repository }}
         tags: |
           type=raw,value=latest,enable=${{ github.ref == format('refs/heads/{0}', github.event.repository.default_branch) }}