Add type ignore until python/typeshed#8716 is released

Author: amyreese

sphinx_mdinclude/sphinx.py

@@ -10,7 +10,9 @@
 from docutils.parsers.rst import directives as rst_directives
 
 try:  # new
-    from docutils.io import error_string as ErrorString
+    from docutils.io import (  # type: ignore  # typeshed  #8716
+        error_string as ErrorString,
+    )
 
     SafeString = str
 except ImportError:  # old