Fix hyperlink rendering in Optax API docs on ReadTheDocs

Currently, the Markdown-flavored links (inside Python files) in Optax API docs (from Python doc strings) appear to not render well on the ReadTheDocs site.

For example, this (source: https://github.com/deepmind/optax/tree/master/optax/_src/alias.py#L322#L374):

def rmsprop(
      ...
) -> base.GradientTransformation:
  """A flexible RMSProp optimiser.
  ...
  References:
    [Tieleman and Hinton, 2012](
        www.cs.toronto.edu/~tijmen/csc321/slides/lecture_slides_lec6.pdf)
    [Graves, 2013](https://arxiv.org/abs/1308.0850)
    ...

translates into this (source: https://optax.readthedocs.io/en/latest/api.html#rmsprop):

Potential solutions:

• Try reStructuredText-flavored formatting for links (since Sphinx likes rST) and see if this fixes the rendering:

`Text <URL>`_

(Source: https://www.sphinx-doc.org/en/master/usage/restructuredtext/basics.html#hyperlinks)

• Alternatively, avoid introducing rST in Python files and, instead, remove Markdown-flavored links ([text](URL)) to keep things simple, like in Haiku docs, since most links are from arXiv and they are quite short:

- [Graves, 2013](https://arxiv.org/abs/1308.0850)
+ Graves, 2013 https://arxiv.org/abs/1308.0850

which is similar to https://dm-haiku.readthedocs.io/en/latest/api.html#id1:

class Linear(hk.Module):
  """Linear module."""

  def __init__(
      ...
  ):
    """Constructs the Linear module.
    Args:
      ...
      w_init: Optional initializer for weights. By default, uses random values
        from truncated normal, with stddev ``1 / sqrt(fan_in)``. See
        https://arxiv.org/abs/1502.03167v3.

LMKWYT @mtthss

I can open a PR 👍

[mkunesch]

Since this has been fixed in #126 I’m closing this issue for now. Thanks for reporting!

[8bitmp3]

@mtthss Let’s try this - from StackOverflow:

  References:
-     Tieleman and Hinton, 2012:
-         www.cs.toronto.edu/~tijmen/csc321/slides/lecture_slides_lec6.pdf
+     Tieleman and Hinton, 2012: www.cs.toronto.edu/~tijmen/csc321/slides/lecture_slides_lec6.pdf # pylint: disable=line-too-long

which should disable pylint=max-line-length=80 for one line only.

https://github.com/deepmind/optax/blob/823af5810cf6af2ee4913771792f42fe24449ee0/.pylintrc#L265

It might help with this TODO: https://github.com/deepmind/optax/blob/823af5810cf6af2ee4913771792f42fe24449ee0/.pylintrc#L267

Also, for multiple lines, this solution could work (based on StackOverflow):

# Disable `pylint` for several lines via `disable` and `enable`: 
# pylint: disable=line-too-long
a_very_long_variable = "Our experiments show that the combination provides state-of-the-art performance on the Atari 2600 benchmark, both in terms of data efficiency and final performance."
another_long_variable = "Pop-Art normalization (van Hasselt et al. 2016) al- lows reward clipping to be removed, while preserving a similar level of performance."
# pylint: enable=line-too-long