Fix xt::ellipsis() usage in numpy doc

Add missing `()` after `ellipsis`

Author: FrancoisDn

docs/source/numpy.rst

@@ -157,7 +157,7 @@ See :any:`numpy indexing <numpy:arrays.indexing>` page.
    +-----------------------------------------+---------------------------------------------------------------------------+
    | ``a[5:1:-1, :]``                        | :cpp:func:`xt::view(a, xt::range(5, 1, -1), xt::all()) <xt::all>`         |
    +-----------------------------------------+---------------------------------------------------------------------------+
-   | ``a[..., 3]``                           | :cpp:func:`xt::strided_view(a, {xt::ellipsis, 3}) <xt::ellipsis>`         |
+   | ``a[..., 3]``                           | :cpp:func:`xt::strided_view(a, {xt::ellipsis(), 3}) <xt::ellipsis>`       |
    +-----------------------------------------+---------------------------------------------------------------------------+
    | :any:`a[:, np.newaxis] <numpy.newaxis>` | :cpp:func:`xt::view(a, xt::all(), xt::newaxis()) <xt::newaxis>`           |
    +-----------------------------------------+---------------------------------------------------------------------------+