[CI] Clean DeepSeek V4 tests and installation scripts (#26609)

docker/Dockerfile

@@ -548,20 +548,12 @@ RUN --mount=type=cache,target=/root/.cache/pip \
 # the `nixl` import path) but unconditionally requires nixl-cu12, so we install
 # it with --no-deps and pair it with the matching nixl-cu12 / nixl-cu13 binary
 # to avoid shipping wrong-CUDA libs on cu13 images.
-# The upstream flash-mla packages are required for running deepseek-v4 models
 RUN --mount=type=cache,target=/root/.cache/pip if [ "${CUDA_VERSION%%.*}" = "12" ]; then \
     python3 -m pip install nixl nixl-cu12 --no-deps ; \
     python3 -m pip install cuda-python==12.9 ; \
-    cd /sgl-workspace && git clone https://github.com/deepseek-ai/FlashMLA.git flash-mla \
-    && cd flash-mla && git submodule update --init --recursive \
-    && pip install --no-build-isolation -v . ; \
 elif [ "${CUDA_VERSION%%.*}" = "13" ]; then \
     python3 -m pip install nixl nixl-cu13 --no-deps ; \
     python3 -m pip install cuda-python==13.2.0 ; \
-    cd /sgl-workspace && git clone https://github.com/deepseek-ai/FlashMLA.git flash-mla \
-    && ln -s /usr/local/cuda/include/cccl/cuda /usr/local/cuda/include/cuda \
-    && cd flash-mla && git submodule update --init --recursive \
-    && pip install --no-build-isolation -v . ; \
 fi
 
 # Add yank script