Rm py38 add setuptools

[bjodah]

just trying to help out on #505

Interestingly: in a container with python 3.13 and no setuptools installed, this command seem to work fine already for the original branch:

root@b6befe24285a# /opt-3/cpython-v3.13.1-release/bin/python3 -c "import setuptools"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
    import setuptools
ModuleNotFoundError: No module named 'setuptools'
root@b6befe24285a# /opt-3/cpython-v3.13.1-release/bin/python3 -c "import distutils"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
    import distutils
ModuleNotFoundError: No module named 'distutils'
root@b6befe24285a# /opt-3/cpython-v3.13.1-release/bin/python3 -m pip install git+https://github.com/isuruf/symengine.py@rm-py38
Collecting git+https://github.com/isuruf/symengine.py@rm-py38
  Cloning https://github.com/isuruf/symengine.py (to revision rm-py38) to /tmp/pip-req-build-1b_frs4q
  Running command git clone --filter=blob:none --quiet https://github.com/isuruf/symengine.py /tmp/pip-req-build-1b_frs4q
  Running command git checkout -b rm-py38 --track origin/rm-py38
  Switched to a new branch 'rm-py38'
  branch 'rm-py38' set up to track 'origin/rm-py38'.
  Resolved https://github.com/isuruf/symengine.py to commit e108841338568d5bc8f2034aa70722d9b221c982
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
  Installing backend dependencies ... done
  Preparing metadata (pyproject.toml) ... done
Building wheels for collected packages: symengine
  Building wheel for symengine (pyproject.toml) ... done
  Created wheel for symengine: filename=symengine-0.14.0-cp313-cp313-linux_x86_64.whl size=11932275 sha256=468a6e4254b78f28a8f07de6f5772236b0832233bdfa5599720b721c9236cefc
  Stored in directory: /tmp/pip-ephem-wheel-cache-mpka22o1/wheels/f9/3c/ff/c53ef4bd800340c08b715f484739615112e23395e8bf62c4e5
Successfully built symengine
Installing collected packages: symengine
Successfully installed symengine-0.14.0