[SYCL][UR] do not expose UR as a backend of SYCL

[smaslov-intel]

No description provided.

[jandres742]

@bader, @smaslov-intel : I'm seeing other PRs failing with the same:

    retcode = call(*popenargs, **kwargs)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python311\Lib\subprocess.py", line 389, in call
    with Popen(*popenargs, **kwargs) as p:
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python311\Lib\subprocess.py", line 1022, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "C:\Python311\Lib\subprocess.py", line 1491, in _execute_child
    hp, ht, pid, tid = _winapi.CreateProcess(executable, args,
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[againull]

SYCL Pre Commit / Windows failure is unrelated and reported. (Presumably started to fail after 26e4493)

[againull]

ESIMD backend failures are not related to this PR and reported.
SYCL :: Basic/memory-consumption.cpp is known - #9008