Fix invalid Docker image tag format

Remove extra slash before the version tag that was causing
"invalid reference format" error in docker buildx.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: zglicz

.github/workflows/docker-a3s.yml

@@ -88,5 +88,5 @@ jobs:
           push: true
           platforms: linux/arm64
           tags: |
-            ${{ steps.login-ecr.outputs.registry }}/a3s/analysis/javascript/:${{ env.BUILD_NUMBER }}
+            ${{ steps.login-ecr.outputs.registry }}/a3s/analysis/javascript:${{ env.BUILD_NUMBER }}
             ${{ steps.login-ecr.outputs.registry }}/a3s/analysis/javascript:latest