COMPAT: remove typing from Graph.describe

[martinfleis]

We don't use types anywhere in the module and these were also using deprecated numpy dtype. Removing for consistency.

Fixes pysal/mapclassify#214

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.1%. Comparing base (bcabdbc) to head (c14f583).
Report is 21 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #719     +/-   ##
=======================================
+ Coverage   85.0%   85.1%   +0.1%     
=======================================
  Files        141     145      +4     
  Lines      15203   15567    +364     
=======================================
+ Hits       12924   13252    +328     
- Misses      2279    2315     +36     

Files	Coverage Δ
libpysal/graph/base.py	96.8% <ø> (-1.1%)	⬇️

... and 6 files with indirect coverage changes