ci(turboquant): drop the ROCm/hipblas build flavor

The TheTom/llama-cpp-turboquant fork is not ROCm-clean at the current pin:
beyond the CUDA-API gaps already patched (3D-peer copy, cudaEventCreate),
its llama.cpp base fails to compile the flash-attention MMA f16 kernels for
head-dim 640 under HIP (cols_per_warp evaluates to 0 -> division-by-zero /
non-constant static asserts in fattn-mma-f16.cuh). That is a deep
ggml-on-ROCm kernel issue, not something a small fork patch can paper over.

Drop -gpu-rocm-hipblas-turboquant from the build matrix so turboquant still
ships for cpu / cublas / vulkan / sycl. Re-add it once the fork's HIP path
compiles (or upstream ggml fixes the large-head-dim MMA kernels for ROCm).

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Assisted-by: Claude:claude-opus-4-8 [Claude Code]

.github/backend-matrix.yml

@@ -1766,20 +1766,6 @@ include:
     dockerfile: "./backend/Dockerfile.llama-cpp"
     context: "./"
     ubuntu-version: '2404'
-  - build-type: 'hipblas'
-    cuda-major-version: ""
-    cuda-minor-version: ""
-    platforms: 'linux/amd64'
-    tag-latest: 'auto'
-    tag-suffix: '-gpu-rocm-hipblas-turboquant'
-    builder-base-image: 'quay.io/go-skynet/ci-cache:base-grpc-rocm-amd64'
-    runs-on: 'ubuntu-latest'
-    base-image: "rocm/dev-ubuntu-24.04:7.2.1"
-    skip-drivers: 'false'
-    backend: "turboquant"
-    dockerfile: "./backend/Dockerfile.turboquant"
-    context: "./"
-    ubuntu-version: '2404'
   - build-type: 'hipblas'
     cuda-major-version: ""
     cuda-minor-version: ""