[misc] Update header year & clearer built-in datasets progress bar msg

[felixdittrich92]

This PR:

• Update header year to 25
• Change built-in datasets progress bar message from "Unpacking" to "Preparing and Loading" to avoid confusion

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.57%. Comparing base (e6bf82d) to head (779eaab).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1831      +/-   ##
==========================================
- Coverage   96.61%   96.57%   -0.04%     
==========================================
  Files         165      165              
  Lines        7939     7940       +1     
==========================================
- Hits         7670     7668       -2     
- Misses        269      272       +3     

Flag	Coverage Δ
unittests	96.57% <100.00%> (-0.04%)	⬇️

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