Upgrade ReadTheDocs build environment to use newer image (#3232)

* documentation: require urllib3<2.0 for now

* moved version requirement to main library in pyproject.toml

* constraint needed in both?

* try upgrading to docbuild with python 3.10, remove restriction on urllib3

* change image -> os

* fixed rtd config

* explicitly added graphviz

---------

Co-authored-by: Naveen M K <naveen521kk@gmail.com>

.readthedocs.yml

@@ -1,11 +1,16 @@
 version: 2
 build:
-  image: latest
+  os: ubuntu-22.04
+
+  tools:
+    python: "3.10"
+
   apt_packages:
     - libpango1.0-dev
     - ffmpeg
+    - graphviz
+
 python:
-   version: 3.8
    install:
       - requirements: docs/rtd-requirements.txt
       - requirements: docs/requirements.txt