* The function ``PyUFunc_GenericFunction`` has been disabled.
  It was deprecated in NumPy 1.19.  Users should call the ufunc
  directly using the Python API.
* The function ``PyUFunc_SetUsesArraysAsData`` has been disabled.
  It was deprecated in NumPy 1.19.

Add release note for Umath C-API deprecations
DOC: Add release note for Umath C-API deprecations

[skip ci]
