Install package deps in readthedocs build (#2465)

Dependencies are required for "automodule" generation.

Co-authored-by: Igor Malinovskiy <igor.malinovskiy@redis.com>
Co-authored-by: Chayim <chayim@users.noreply.github.com>

.readthedocs.yml

@@ -3,6 +3,7 @@ version: 2
 python:
   install:
     - requirements: ./docs/requirements.txt
+    - requirements: requirements.txt
 
 build:
   os: ubuntu-20.04