Bump to NLPModels 0.21

[tmigot]

[github-actions[bot]]

Package name	latest	stable
FletcherPenaltySolver.jl
Percival.jl

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 86.66%. Comparing base (1e1368e) to head (f084219). Report is 3 commits behind head on main.

:exclamation: Current head f084219 differs from pull request most recent head b5a4605. Consider uploading reports for the commit b5a4605 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #277   +/-   ##
=======================================
  Coverage   86.66%   86.66%           
=======================================
  Files           7        7           
  Lines        1125     1125           
=======================================
  Hits          975      975           
  Misses        150      150           

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