docs: fix duplicated word in dlnss_dlnr docstring

[steven-murray]

Summary

• Fixes a small typo ("the the" → "the") in the dlnss_dlnr docstring in src/hmf/density_field/filters.py.

Test plan

• Docs-only change, no functional code affected.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.86%. Comparing base (a72a936) to head (bf22040).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #315   +/-   ##
=======================================
  Coverage   97.86%   97.86%           
=======================================
  Files          26       26           
  Lines        2671     2671           
=======================================
  Hits         2614     2614           
  Misses         57       57           

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