[Backport release-1.15][c++] Simplify C++ copyright headers

[johnkerl]

Issue and/or context: Manually backport #3619 to the release-1.15 branch given #3619 (comment)

Changes:

Notes for Reviewer:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.35%. Comparing base (9843f18) to head (c815e1b).
Report is 2 commits behind head on release-1.15.

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.15    #3660      +/-   ##
================================================
+ Coverage         86.30%   86.35%   +0.04%     
================================================
  Files                55       55              
  Lines              6381     6381              
================================================
+ Hits               5507     5510       +3     
+ Misses              874      871       -3     

Flag	Coverage Δ
python	86.35% <ø> (+0.04%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
python_api	86.35% <ø> (+0.04%)	⬆️
libtiledbsoma	∅ <ø> (∅)

[jp-dark]

No new code should be added in this PR. The following files should be added by a different backport:

• soma_column.{cc,h}
• soma_dimension.{cc,h}
• soma_geometry_column.{cc,h}
• uni_soma_column.cc

[johnkerl]

Thanks @jp-dark ! c815e1b