use existing project url for now

pyproject.toml

@@ -50,7 +50,7 @@ tests = [
   "pytest-remotedata",
 ]
 [project.urls]
-'documentation' = 'https://www.asdf-format.org/projects/asdf/en/latest'
+'documentation' = 'https://asdf.readthedocs.io/en/stable/'
 'repository' = 'https://github.com/asdf-format/asdf'
 'tracker' = 'https://github.com/asdf-format/asdf/issues'
 [project.entry-points]