ci: remove redundant environment variable setting

Author: cpcloud

ci/tools/env-vars

@@ -38,7 +38,6 @@ echo "PYTHON_VERSION_FORMATTED=${PYTHON_VERSION_FORMATTED}" >> $GITHUB_ENV
 
 if [[ "${1}" == "build" ]]; then
   echo "CIBW_BUILD=${CIBW_BUILD}" >> $GITHUB_ENV
-  echo "CIBW_ENABLE=cpython-freethreading" >> $GITHUB_ENV
   CUDA_BINDINGS_ARTIFACT_BASENAME="cuda-bindings-python${PYTHON_VERSION_FORMATTED}-cuda${CUDA_VER}-${HOST_PLATFORM}"
 elif [[ "${1}" == "test" ]]; then
   BUILD_CUDA_MAJOR="$(cut -d '.' -f 1 <<< ${BUILD_CUDA_VER})"