drop linkchecking

docs/check_sphinx.py

 import pytest
 import subprocess
 
-def test_linkcheck(tmpdir):
-    doctrees = tmpdir.join("doctrees")
-    htmldir = tmpdir.join("html")
-    subprocess.check_call(
-        ["sphinx-build", "-q", "-blinkcheck",
-          "-d", str(doctrees), ".", str(htmldir)])
-
 def test_build_docs(tmpdir):
     doctrees = tmpdir.join("doctrees")
     htmldir = "html" #we want to keep the docs