Update RELEASING.md

[willingc]

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[codecov-commenter]

Codecov Report

Merging #47 (dff657e) into main (71313c8) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #47   +/-   ##
=======================================
  Coverage   94.58%   94.58%           
=======================================
  Files           8        8           
  Lines         499      499           
=======================================
  Hits          472      472           
  Misses         27       27           

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[kafonek]

Should consider using from importlib_metadata import version; __version__ = version(__package__) in sending/__init__.py so we don't need to bump versions in two places.