docs: fixing the readthedocs builds

.readthedocs.yaml

@@ -6,10 +6,10 @@
 version: 2
 
 # Set the version of Python and other tools you might need
-#build:
-  #os: ubuntu-20.04
-  #tools:
-    #python: "3.9"
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "mambaforge-22.9"
     # You can also specify other tool versions:
     # nodejs: "16"
     # rust: "1.55"

host/docs/sphinx/environment.yml

@@ -3,5 +3,7 @@ channels:
   - conda-forge
   - defaults
 dependencies:
+   - pip
   - cmake
   - compilers
+  - sphinx=5.3