Correctly created default_context for non-Linux platforms

Replaced `default_context = None` with
`default_context = dpctl.SyclQueue(root_device).sycl_context`
in `from_dlpack_capsule` for non-Linux platforms

Author: oleksandr-pavlyk

dpctl/tensor/_dlpack.pyx

@@ -340,7 +340,7 @@ cpdef usm_ndarray from_dlpack_capsule(object py_caps) except +:
             if _IS_LINUX:
                 default_context = root_device.sycl_platform.default_context
             else:
-                default_context = None
+                default_context = dpctl.SyclQueue(root_device).sycl_context
         except RuntimeError:
             default_context = dpctl.SyclQueue(root_device).sycl_context
         if dlm_tensor.dl_tensor.data is NULL: