Fix broken links

Author: ddomingof

docs/source/conf.py

@@ -56,9 +56,7 @@
 # Example configuration for intersphinx: refer to the Python standard library.
 intersphinx_mapping = {
     'python': ('https://docs.python.org/3', None),
-    'networkx': ('https://networkx.github.io/', None),
-    'sqlalchemy': ('https://docs.sqlalchemy.org/en/latest', None),
-    'pybel': ('https://pybel.readthedocs.io/en/latest/', None),
+    'networkx': ('https://networkx.github.io/documentation/stable', None),
 }
 
 autodoc_member_order = 'bysource'