📦 Update/remove `kiwipy` depedency

[mbercx]

Our current version specifier of plumpy

https://github.com/aiidateam/aiida-core/blob/1f2cb47cfe1821af170170be451506977cf1348a/pyproject.toml#L42

would install the new plumpy==0.25.1, whose main change is to bump it's kiwipy version to ~=0.9.0 to get the "hotfix of aiormq" via the aio-pika dependency. However, since we also specify kiwipy in the aiida-core dependencies as:

https://github.com/aiidateam/aiida-core/blob/1f2cb47cfe1821af170170be451506977cf1348a/pyproject.toml#L46

pip will simply resolve to the old plumpy version:

❯ pip install aiida-core~=2.7.1 --dry-run
...
Would install aiida-core-2.7.1 kiwipy-0.8.5 plumpy-0.25.0

@unkcpz do you know why we specify the kiwipy dependency directly at all? If we can't simply remove it, I suppose we should update it to ~=0.9.0 to benefit from the hotfix you made.