[Bugfix] fix gpu docker image mis benchmarks dir (#16628)

Signed-off-by: rongfu.leng <rongfu.leng@daocloud.io>

docker/Dockerfile

@@ -240,6 +240,7 @@ if [ "$TARGETPLATFORM" != "linux/arm64" ]; then \
     uv pip install --system https://github.com/flashinfer-ai/flashinfer/releases/download/v0.2.1.post2/flashinfer_python-0.2.1.post2+cu124torch2.6-cp38-abi3-linux_x86_64.whl ; \
 fi
 COPY examples examples
+COPY benchmarks benchmarks
 
 # Although we build Flashinfer with AOT mode, there's still
 # some issues w.r.t. JIT compilation. Therefore we need to