Fix some typos in release instructions

[kevin-bates]

While looking into adopting recent build framework changes in another repo, I ran into a couple of (minor) issues with the recently-added hatchling instructions. I also took the liberty to update the variable script_version to new_version to have parity with its prompt (as well as dev_version).

[codecov-commenter]

Codecov Report

Base: 72.59% // Head: 72.59% // No change to project coverage 👍

Coverage data is based on head (613ffc7) compared to base (5eb977c).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1003   +/-   ##
=======================================
  Coverage   72.59%   72.59%           
=======================================
  Files          64       64           
  Lines        8249     8249           
  Branches     1378     1378           
=======================================
  Hits         5988     5988           
  Misses       1847     1847           
  Partials      414      414           

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[blink1073]

Thanks!