Double backticks with spaces aren't rendered properly

[NicolasHug]

It is sometimes useful to write code-like bits in the docs, and we use double backticks for that. Those bits may contain spaces, and currently the spaces will be rendered as the regular background instead of the grey-ish background. For example:

        boxes (Tensor[N, 4]): boxes in ``(x1, y1, x2, y2)`` format
            with ``0 <= x1 < x2`` and ``0 <= y1 < y2``.

Is rendered as:

link: https://pytorch.org/vision/stable/ops.html#torchvision.ops.nms

There are occurrences in the pytorch docs as well: https://pytorch.org/docs/stable/tensors.html#torch.Tensor.where

It would be nice to have a uniform background instead, that isn't divided by the spaces.