[MNT] Delete legacy residuals.py module

[fkiraly]

This PR removes the legacy residuals.py module, it is superseded by the ResidualDouble estimator.

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: -0.33% ⚠️

Comparison is base (721549c) 71.38% compared to head (70a30a3) 71.06%.
Report is 1 commits behind head on main.

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #77      +/-   ##
==========================================
- Coverage   71.38%   71.06%   -0.33%     
==========================================
  Files          92       91       -1     
  Lines        4945     4862      -83     
  Branches      897      892       -5     
==========================================
- Hits         3530     3455      -75     
- Misses       1180     1186       +6     
+ Partials      235      221      -14     

see 5 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.