[DEL] Remove long_description_content_type

Author: f-dangel

setup.cfg

@@ -10,7 +10,6 @@ author = Felix Dangel
 author_email = fdangel@vectorinstitute.ai
 license = MIT
 long_description = Convolutions as tensor contractions (einsums) for PyTorch
-long_description_content_type="text/markdown"
 keywords = convolution, einsum, tensor networks, einconv
 # Change if running only on Windows, Mac or Linux (comma-separated)
 platforms = any