[CI] Bump docker/metadata-action from 5 to 6 (#7069)

Bumps [docker/metadata-action](https://github.com/docker/metadata-action) from 5 to 6.


- vLLM version: v0.16.0
- vLLM main:
4034c3d32e

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/_schedule_image_build.yaml

@@ -139,7 +139,7 @@ jobs:
 
       - name: Docker meta
         id: meta
-        uses: docker/metadata-action@v5
+        uses: docker/metadata-action@v6
         with:
           # TODO(yikun): add more hub image and a note on release policy for container image
           images: |

.github/workflows/schedule_lint_image_build.yaml

@@ -38,7 +38,7 @@ jobs:
         lscpu
     - name: Docker meta
       id: meta
-      uses: docker/metadata-action@v5
+      uses: docker/metadata-action@v6
       with:
         images: |
           quay.io/ascend-ci/vllm-ascend