Clean up DPCTL_TARGET_CUDA handling

Author: vlad-perevezentsev

CMakeLists.txt

@@ -55,10 +55,6 @@ set(_dpctl_amd_targets)
 if ("x${DPCTL_SYCL_TARGETS}" STREQUAL "x")
    if (DPCTL_TARGET_CUDA)
       set(_dpctl_sycl_targets "nvptx64-nvidia-cuda,spir64-unknown-unknown")
-   else()
-      if (DEFINED ENV{DPCTL_TARGET_CUDA})
-          set(_dpctl_sycl_targets "nvptx64-nvidia-cuda,spir64-unknown-unknown")
-      endif()
    endif()
    if (NOT "x${DPCTL_TARGET_HIP}" STREQUAL "x")
       set(_dpctl_amd_targets ${DPCTL_TARGET_HIP})