[doc] update readthedocs settings by using the latest build options and remove legacy syntax

.readthedocs.yml

@@ -7,7 +7,9 @@ version: 2
 
 # Specify docker image for building the doc
 build:
-  image: latest
+  os: ubuntu-22.04
+  tools:
+    python: "3.7"
 
 # Build documentation in the docs/ directory with Sphinx
 sphinx:
@@ -19,7 +21,8 @@ formats: all
 
 # Optionally set the version of Python and requirements required to build your docs
 python:
-  version: 3.7
   system_packages: true
   install:
     - requirements: docs/requirements.txt
+    - method: pip
+      path: .