Remove deprecated things

[dpanici]

• DESC/desc/equilibrium/coords.py

  Line 769 in 95612fa

  # TODO: deprecated, remove eventually

• DESC/desc/input_reader.py

  Line 347 in 2741269

  DeprecationWarning("nfev is deprecated, please use maxiter instead")

• DESC/desc/objectives/objective_funs.py

  Line 246 in 2741269

  '``deriv_mode="looped"`` is deprecated in favor of'

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