Updated CHANGELOG

This file documents major changes to PICOS. The format is based on

`Keep a Changelog <https://keepachangelog.com/en/1.0.0/>`_.

.. _Unreleased: https://gitlab.com/picos-api/picos/compare/v2.4...master

.. _2.4: https://gitlab.com/picos-api/picos/compare/v2.3...v2.4

.. _2.3: https://gitlab.com/picos-api/picos/compare/v2.2...v2.3

.. _2.2: https://gitlab.com/picos-api/picos/compare/v2.1...v2.2

.. _0.1.0: about:blank

`Unreleased`_

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*The quantum relative entropy update.*

.. rubric:: Added

- Support for QICS, a new conic solver which supports solving LP, SOCP, SDP, 

  EXP, as well as a new class of problems called quantum relative entropy 

  programs (QREP). 

- New expressions for quantum entropic and nonlinear matrix-valued functions, 

  including arising in quantum information theory, as well as constraints

  representing the epigraphs or hypographs of these functions. These include

  - Quantum entropy (:fun:`picos.quantentr`),

  - Quantum relative entropy (:fun:`picos.quantrelentr`),

  - Quantum conditional entropy (:fun:`picos.quantcondentr`),

  - Operator relative entropy (:fun:`picos.oprelentr`), and

  - Matrix geometric mean (:fun:`picos.mtxgeomean`).

- Updated documentation with examples solving quantum relative entropy programs.

- Added test examples for new quantum entropy and non-commutative perspective

  functions.

.. rubric:: Changed

- Updated :class:`picos.constraints.con_kldiv.KullbackLeiblerConstraint` so that

  it can be used as a constraint without having to convert to the exponential

  cone.

.. rubric:: Fixed

- Changed linter CI to use ruff instead of pylama.

- Fixed Gurobi Legacy interface for rotated second order cone.

- Fixed :fun:`picos.patch_scipy_array_priority` which was failing doctests.

- Fixed doctest for :fun:`picos.Problem.add_variable`.

- Fixed issue where :class:`~picos.expressions.exp_wsum.WeightedSum` wasn't 

  working for a single weighted expression.

.. rubric:: Deprecated

- Depreciated ``rng`` argument in :fun:`picos.expressions.Samples.shuffled`,

  which is no longer a parameter in :fun:`random.shuffle` as of Python 3.11.

`2.4`_ - 2022-02-12

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