RTD config update

[kanekosh]

Purpose

RTD recently deprecated python.system_packages: https://blog.readthedocs.com/drop-support-system-packages/
This PR removes the above key from the RTD yaml file. I don't think this will affect the documentation build process.

Type of change

What types of change is it?
Select the appropriate type(s) that describe this PR

• Maintenance update

Testing

Explain the steps needed to test the new code to verify that it does indeed address the issue and produce the expected behavior.

Checklist

Put an x in the boxes that apply.

• I have run unit and regression tests which pass locally with my changes
• I have added new tests that prove my fix is effective or that my feature works
• I have added necessary documentation

[codecov]

Codecov Report

Merging #56 (7348c54) into main (ee4aa68) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #56   +/-   ##
=======================================
  Coverage   79.99%   79.99%           
=======================================
  Files          85       85           
  Lines        9297     9297           
=======================================
  Hits         7437     7437           
  Misses       1860     1860           

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more