build(deps): Bump docker/metadata-action from 5 to 6

Bumps [docker/metadata-action](https://github.com/docker/metadata-action) from 5 to 6.
- [Release notes](https://github.com/docker/metadata-action/releases)
- [Commits](https://github.com/docker/metadata-action/compare/v5...v6)

---
updated-dependencies:
- dependency-name: docker/metadata-action
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/containers.yml

@@ -188,7 +188,7 @@ jobs:
 
       - name: Docker meta
         id: meta
-        uses: docker/metadata-action@v5
+        uses: docker/metadata-action@v6
         with:
           images: |
             ghcr.io/openwrt/imagebuilder
@@ -280,7 +280,7 @@ jobs:
 
       - name: Docker meta (tag or branch)
         id: meta_ref
-        uses: docker/metadata-action@v5
+        uses: docker/metadata-action@v6
         with:
           images: |
             ghcr.io/openwrt/sdk
@@ -294,7 +294,7 @@ jobs:
 
       - name: Docker meta (version)
         id: meta_version
-        uses: docker/metadata-action@v5
+        uses: docker/metadata-action@v6
         with:
           images: |
             ghcr.io/openwrt/sdk
@@ -309,7 +309,7 @@ jobs:
       - name: Docker meta (master)
         if: needs.generate_matrix.outputs.ref == 'main'
         id: meta_master
-        uses: docker/metadata-action@v5
+        uses: docker/metadata-action@v6
         with:
           images: |
             ghcr.io/openwrt/sdk
@@ -324,7 +324,7 @@ jobs:
       - name: Docker meta (target and arch)
         if: needs.generate_matrix.outputs.version == 'SNAPSHOT'
         id: meta_target_arch
-        uses: docker/metadata-action@v5
+        uses: docker/metadata-action@v6
         with:
           images: |
             ghcr.io/openwrt/sdk
@@ -338,7 +338,7 @@ jobs:
       - name: Docker meta (latest)
         if: needs.generate_matrix.outputs.version == 'SNAPSHOT' && matrix.target == 'x86/64'
         id: meta_latest
-        uses: docker/metadata-action@v5
+        uses: docker/metadata-action@v6
         with:
           images: |
             ghcr.io/openwrt/sdk
@@ -447,7 +447,7 @@ jobs:
 
       - name: Docker meta
         id: meta
-        uses: docker/metadata-action@v5
+        uses: docker/metadata-action@v6
         with:
           images: |
             ghcr.io/openwrt/rootfs