Merge pull request #757 from benjeffery/fix-pypi

Fix readme MIME for PyPI

Author: benjeffery

setup.cfg

@@ -4,7 +4,7 @@ author= Tskit Developers
 author_email = [email protected]
 license = GNU GPLv3+
 description= Infer tree sequences from genetic variation data.
-long_description_content_type = text/x-markdown
+long_description_content_type = text/markdown
 long_description = file: README.md
 url = https://tskit.dev/tsinfer
 project_urls =