REF: remove result_index attribute from describe_agg

[u3ks]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.0%. Comparing base (4037c70) to head (bb26c47).
Report is 61 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #626     +/-   ##
=======================================
+ Coverage   97.4%   98.0%   +0.6%     
=======================================
  Files         26      38     +12     
  Lines       4328    6217   +1889     
=======================================
+ Hits        4214    6091   +1877     
- Misses       114     126     +12     

Files	Coverage Δ
momepy/functional/_diversity.py	96.6% <100.0%> (ø)
momepy/functional/tests/test_diversity.py	100.0% <100.0%> (ø)
momepy/functional/tests/test_intensity.py	100.0% <100.0%> (ø)