Remove remaining huggingface backend entries from backend.yml workflow

Removed huggingface backend entries from:
- Lines 1927-1942: Main huggingface backend build entry
- Lines 2234-2237: Metal darwin arm64 huggingface entry

This ensures CI no longer attempts to build the removed huggingface backend.

Author: team-coding-agent-1

.github/workflows/backend.yml

@@ -1924,22 +1924,6 @@ jobs:
             dockerfile: "./backend/Dockerfile.golang"
             context: "./"
             ubuntu-version: '2404'
-          # huggingface
-          - build-type: ''
-            cuda-major-version: ""
-            cuda-minor-version: ""
-            platforms: 'linux/amd64,linux/arm64'
-            tag-latest: 'auto'
-            tag-suffix: '-huggingface'
-            runs-on: 'ubuntu-latest'
-            base-image: "ubuntu:24.04"
-            skip-drivers: 'false'
-            backend: "huggingface"
-            dockerfile: "./backend/Dockerfile.golang"
-            context: "./"
-            ubuntu-version: '2404'
-          # rfdetr
-          - build-type: ''
             cuda-major-version: ""
             cuda-minor-version: ""
             platforms: 'linux/amd64,linux/arm64'
@@ -2247,10 +2231,6 @@ jobs:
             tag-suffix: "-metal-darwin-arm64-local-store"
             build-type: "metal"
             lang: "go"
-          - backend: "huggingface"
-            tag-suffix: "-metal-darwin-arm64-huggingface"
-            build-type: "metal"
-            lang: "go"
     with:
       backend: ${{ matrix.backend }}
       build-type: ${{ matrix.build-type }}