Remove redundant registry retrieval step and use environment variable directly in Docker workflow

Signed-off-by: Stephen Simpson <ssimpson89@users.noreply.github.com>

.gitea/workflows/docker-image-linux.yml

@@ -21,21 +21,6 @@ jobs:
       packages: write
 
     steps:
-      - name: Get Registry
-        id: registry
-        run: |
-          # Use RUNNER_REGISTRY environment variable
-          if [ ! -z "${RUNNER_REGISTRY}" ]; then
-            REGISTRY="${RUNNER_REGISTRY}"
-          else
-            echo "ERROR: RUNNER_REGISTRY environment variable not set"
-            echo "Please add RUNNER_REGISTRY to your runner's environment variables"
-            exit 1
-          fi
-          
-          echo "registry=${REGISTRY}" >> $GITHUB_OUTPUT
-          echo "Using registry: ${REGISTRY}"
-
       - name: Checkout code
         uses: actions/checkout@v4
 
@@ -48,7 +33,7 @@ jobs:
       - name: Log in to registry
         uses: docker/login-action@v3
         with:
-          registry: ${{ steps.registry.outputs.registry }}
+          registry: ${{ vars.REGISTRY }}
           username: ${{ vars.USERNAME }}
           password: ${{ secrets.PASS }}
 
@@ -56,7 +41,7 @@ jobs:
         id: meta
         uses: docker/metadata-action@v5
         with:
-          images: ${{ steps.registry.outputs.registry }}/${{ vars.USERNAME }}/${{ env.IMAGE_NAME }}
+          images: ${{ vars.REGISTRY }}/${{ vars.USERNAME }}/${{ env.IMAGE_NAME }}
           tags: |
             # Only tag with version and latest on tag push
             type=semver,pattern={{version}},enable=${{ startsWith(github.ref, 'refs/tags/') }}