Update license headers

[BrownianNotion]

Resolves: #18710

Updated license headers. Wasn't sure about copyright year so I defaulted to 2024. Note that some files not listed in the original issue (eg. sandbox/engraving/log.h) have the correct license but an old copyright year.

TODO:

• Remove === lines and replace // comments with /**/

• I signed the CLA
• The title of the PR describes the problem it addresses
• Each commit's message describes its purpose and effects, and references the issue it resolves
• If changes are extensive, there is a sequence of easily reviewable commits
• The code in the PR follows the coding rules
• There are no unnecessary changes
• The code compiles and runs on my machine, preferably after each commit individually
• I created a unit test or vtest to verify the changes I made (if applicable)

[cbjeukendrup]

For consistency with more recently added files, I suggest two things:

• remove those ===================================================================== lines
• In engraving/sandbox.h and tools/bww2html/mxmlwriter.h, use /* */ comments (like for example in src/app/main.cpp) instead of //.
  (This is useful because some IDEs recognise copyright comments at the top of a file, and when it's a /* */ comment it is collapsed automatically.)

[BrownianNotion]

For consistency with more recently added files, I suggest two things:

• remove those ===================================================================== lines
• In engraving/sandbox.h and tools/bww2html/mxmlwriter.h, use /* */ comments (like for example in src/app/main.cpp) instead of //.
  (This is useful because some IDEs recognise copyright comments at the top of a file, and when it's a /* */ comment it is collapsed automatically.)

Changed! Have left the === lines in the .xml files to be consistent with the rest of the file.

[cbjeukendrup]

Thanks, that looks good!

[cbjeukendrup]

One more question: what username on MuseScore.org did you use to sign the CLA?

[BrownianNotion]

One more question: what username on MuseScore.org did you use to sign the CLA?

Username was andrewwusyd (my bio has a url to this github :) ).