readthedocs: include all submodules

Signed-off-by: Johan Euphrosine <proppy@google.com>

.readthedocs.yaml

diff --git a/.readthedocs.yaml b/.readthedocs.yaml
index 3d4914b..544bab8 100644
--- a/.readthedocs.yaml
+++ b/.readthedocs.yaml
@@ -24,9 +24,7 @@
   - requirements: docs/requirements.txt
 
 submodules:
-  include:
-  - third_party/open-source-pdks
-  recursive: false
+  include: all
 
 formats:
   - pdf