Remove sphinx from the list of integration tests

It seems that they migrated to `flit` and no longer use setuptools.

Author: abravalheri

setuptools/tests/integration/test_pip_install_sdist.py

@@ -42,7 +42,6 @@
 # due to their relevance to the numerical/scientific programming ecosystem)
 EXAMPLES = [
     ("pandas", LATEST),  # cython + custom build_ext
-    ("sphinx", LATEST),  # custom setup.py
     ("pip", LATEST),  # just in case...
     ("pytest", LATEST),  # uses setuptools_scm
     ("mypy", LATEST),  # custom build_py + ext_modules