docs: clarify unreleased whatsnew details

[bjlittle]

🚀 Pull Request

Description

This pull-request clarifies the unreleased whatsnew announcement and highlights section details as TBD prior to release.

This also backs-up the in-progress status from the stated development version i.e., vX.devX.

This is more appropriate than stating N/A in these sections.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.28%. Comparing base (1c0c2d2) to head (66ede0e).
Report is 129 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1058   +/-   ##
=======================================
  Coverage   91.28%   91.28%           
=======================================
  Files          58       58           
  Lines        2936     2936           
=======================================
  Hits         2680     2680           
  Misses        256      256           

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