Setup: remove setup.py since setuptools 64 supports pep660 now

[MuellerSeb]

Solves issue mentioned in #287

[coveralls]

Pull Request Test Coverage Report for Build 3000252505

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.04%) to 77.712%

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Files with Coverage Reduction	New Missed Lines	%
src/spotpy/algorithms/demcz.py	2	89.84%
<!--	Total:	2		-->

Totals
Change from base Build 2717470960:	-0.04%
Covered Lines:	4177
Relevant Lines:	5375

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💛 - Coveralls

[thouska]

Super cool, thank you for keeping this up-to-date!