Update esmvalcore dependency to 2.4.0rc1

[zklaus]

Description

Update dependencies in environment.yml and setup.py

---

Checklist

It is the responsibility of the author to make sure the pull request is ready to review. The icons indicate whether the item will be subject to the 🛠 Technical or 🧪 Scientific review.

• 🛠 This pull request has a descriptive title
• 🛠 Code is written according to the code quality guidelines
• 🛠 Documentation is available
• 🛠 Tests run successfully
• 🛠 The list of authors is up to date
• 🛠 Any changed dependencies have been added or removed correctly
• 🛠 All checks below this pull request were successful

---

To help with the number of pull requests:

• 🙏 We kindly ask you to review two other open pull requests in this repository

[valeriupredoi]

@zklaus nice work, I like the riddance of all those antiquated pins! The good news is that the conda env solves well and fast on the GA machine and we should get #2344 in here then I reckon we'll be in business. There is the Circle tests issue, but let's plug in mamba there 😁

[valeriupredoi]

here's another thing - the editable pip installation worked for me with pip=21.3 after having created a mamba environment with this PR:

valeriu@valeriu-PORTEGE-Z30-C:~/ESMValTool$ conda list python
# packages in environment at /home/valeriu/miniconda3-fresh/envs/core24rc1:
#
# Name                    Version                   Build  Channel
antlr-python-runtime      4.7.2           py39hf3d152e_1002    conda-forge
magics-python             1.5.6              pyhd8ed1ab_0    conda-forge
msgpack-python            1.0.2            py39h1a9c180_1    conda-forge
python                    3.9.7           hb7a2778_3_cpython    conda-forge
python-dateutil           2.8.2              pyhd8ed1ab_0    conda-forge
python-stratify           0.2.post0        py39hce5d2b2_0    conda-forge
python-xxhash             2.0.2            py39h3811e60_0    conda-forge
python_abi                3.9                      2_cp39    conda-forge
valeriu@valeriu-PORTEGE-Z30-C:~/ESMValTool$ conda list pip
# packages in environment at /home/valeriu/miniconda3-fresh/envs/core24rc1:
#
# Name                    Version                   Build  Channel
pip                       21.3               pyhd8ed1ab_0    conda-forge

EDIT agh nevermind, I forgot to blow up me eggs 🥚 All's good - it fails as per normal - the eggs were leftover from #2344

[valeriupredoi]

btw forgot to say - I have done some unpinning in #2327 a wee back ago, but chose to pin iris to latest, now that we have it pinned in Core all's fine and I can close that 👍

[valeriupredoi]

@zklaus very cool, man! I went through the GA tests, specifically looking at the environments for each platform/OS and Python version - all consistent, and modern, and the usual suspects (nc-time-axis, esmpy, mpich etc) are all nice and modern and looking like not being troublemakers; am gonna remove the test branches in the GA workflows and approve 👍 🍺