[DOC] Fix doc-rules build

Doc-rules build is failing due to changes expected in .readthedocs.yaml
file.  Updated this file as needed to pass that build.

Issue-ID: DOC-811
Signed-off-by: Dan Timoney <dtimoney@att.com>
Change-Id: Id072195a06178824803d5550ddbcaf3949c03d8b
diff --git a/.readthedocs.yaml b/.readthedocs.yaml
index 40e9e99..540143f 100644
--- a/.readthedocs.yaml
+++ b/.readthedocs.yaml
@@ -7,15 +7,13 @@
 version: 2
 
 build:
-   image: latest
+  os: ubuntu-20.04
+  tools:
+    python: "3.8"
 
 python:
-   version: 3.7
    install:
       - requirements: docs/requirements-docs.txt
 
-submodules:
-   include: all
-
 sphinx:
-   configuration: docs/conf.py
\ No newline at end of file
+   configuration: docs/conf.py