Upload to PyPI fails because of malformed README.rst file

$ poetry build
Building AlekSIS-App-Alsijil (2.0rc8)
  - Building sdist
  - Built AlekSIS-App-Alsijil-2.0rc8.tar.gz
  - Building wheel
  - Built AlekSIS_App_Alsijil-2.0rc8-py3-none-any.whl
$ twine check dist/*
Checking dist/AlekSIS_App_Alsijil-2.0rc8-py3-none-any.whl: FAILED
  `long_description` has syntax errors in markup and would not be rendered on PyPI.
    line 7: Error: Unknown target name: "aleksis®".
Checking dist/AlekSIS-App-Alsijil-2.0rc8.tar.gz: FAILED
  `long_description` has syntax errors in markup and would not be rendered on PyPI.
    line 7: Error: Unknown target name: "aleksis®".