update doc requirements

Author: bmtgoncalves

.readthedocs.yaml

@@ -21,12 +21,12 @@ sphinx:
 
 # Optionally build your docs in additional formats such as PDF and ePub
 # formats:
-#    - pdf
-#    - epub
+    - pdf
+    - epub
 
 # Optional but recommended, declare the Python requirements required
 # to build your documentation
 # See https://docs.readthedocs.io/en/stable/guides/reproducible-builds.html
-# python:
-#    install:
-#    - requirements: docs/requirements.txt
+python:
+   install:
+   - requirements: docs/requirements.txt