Update copyright

[nhniina]

Update copyright from " Copyright (C) 2017 - 2023 Spine Project" and its variations to

Copyright (C) 2017 - 2021 Spine project consortium
Copyright SpineOpt contributors

Checklist before merging

• Documentation is up-to-date
• Unit tests have been added/updated accordingly
• Code has been formatted according to SpineOpt's style
• Unit tests pass

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.37%. Comparing base (bb476d9) to head (476a2c7).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1191   +/-   ##
=======================================
  Coverage   87.37%   87.37%           
=======================================
  Files         144      144           
  Lines        4443     4443           
=======================================
  Hits         3882     3882           
  Misses        561      561           

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[Tasqu]

Thanks 👍