Update .readthedocs.yaml python version to 3.7 (#6893)

Changed the python version to 3.7 to address ReadTheDocs build problems

Author: MattRoweEAIF

.readthedocs.yaml

@@ -9,7 +9,7 @@ version: 2
 build:
   os: ubuntu-22.04
   tools:
-    python: "3.12"
+    python: "3.7"
 
 mkdocs:
   configuration: mkdocs.yml
@@ -18,4 +18,4 @@ mkdocs:
 
 python:
   install:
-  - requirements: Docs/requirements.txt
+  - requirements: Docs/requirements.txt