ci: drop arm64 from GPU build — use :cpu for arm64 instead

.github/workflows/docker-publish.yml

@@ -36,15 +36,13 @@ env:
 
 jobs:
   build:
-    name: Build (${{ matrix.platform }})
+    name: Build (linux/amd64)
-    runs-on: ${{ matrix.runner }}
+    runs-on: ubuntu-latest
     strategy:
       matrix:
         include:
           - platform: linux/amd64
             runner: ubuntu-latest
-          - platform: linux/arm64
-            runner: ubuntu-latest
     permissions:
       contents: read
       packages: write
@@ -63,10 +61,6 @@ jobs:
         with:
           ref: ${{ inputs.tag || github.ref }}
 
-      - name: Set up QEMU
-        if: matrix.platform == 'linux/arm64'
-        uses: docker/setup-qemu-action@v4
-
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v4
 
@@ -108,7 +102,7 @@ jobs:
       - name: Upload digest
         uses: actions/upload-artifact@v4
         with:
-          name: digest-${{ matrix.platform == 'linux/amd64' && 'amd64' || 'arm64' }}
+          name: digest-amd64
           path: /tmp/digests/*
           if-no-files-found: error
           retention-days: 1