socket: rename nng_close to nng_socket_close

[gdamore]

fixes #

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.73%. Comparing base (9c64c3a) to head (b0874b1).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2044   +/-   ##
=======================================
  Coverage   82.73%   82.73%           
=======================================
  Files          95       95           
  Lines       23770    23770           
  Branches     3068     3068           
=======================================
  Hits        19667    19667           
  Misses       4027     4027           
  Partials       76       76           

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