Test docs build without notebooks

Author: daquinteroflex

.gitmodules

@@ -1,6 +1,3 @@
-[submodule "docs/notebooks"]
-	path = docs/notebooks
-	url = [email protected]:flexcompute/tidy3d-notebooks.git
 [submodule "docs/faq"]
 	path = docs/faq
 	url = https://github.com/flexcompute/tidy3d-faq

docs/index.rst

@@ -179,7 +179,7 @@ Further Information
 
   install
   lectures/index
-  notebooks/docs/index
+  Example Library <https://flexcompute-tidy3d-notebooks-docs.readthedocs-hosted.com/en/demo-test-self_contained_notebooks/>
   faq/docs/index
   api/index
   development/index