Update .readthedocs.yml

Path to the conf.py was wrong! Updating now and Python version to 3.9
This explains why previous read the docs have been failing.

Author: julesghub

.readthedocs.yml

@@ -7,14 +7,14 @@ version: 2
 
 # Build documentation in the docs/ directory with Sphinx
 sphinx:
-  configuration: docs/readthedocs/source/conf.py
+  configuration: docs/readthedocs/src/conf.py
 
 # Optionally build your docs in additional formats such as PDF
 formats:
   - pdf
 
 # Optionally set the version of Python and requirements required to build your docs
 python:
-  version: 3.7
+  version: 3.9
   install:
     - requirements: docs/readthedocs/requirements.txt