Update pyproject.toml

Author: kmuehlbauer

pyproject.toml

@@ -35,7 +35,7 @@ repository = "https://github.com/wradlib/wradlib-data"
 
 [tool.setuptools.dynamic]
 dependencies = { file = ["requirements.txt"] }
-readme = { file = ["README.md"], content_type = "text/markdown" }
+readme = { file = ["README.md"], content-type = "text/markdown" }
 
 [tool.setuptools]
 packages = ["wradlib_data", "wradlib_data.tests"]