Fix: years without spaces

[Gootector]

Years without spaces - like "Copyright © 1999-2023 MuseScore BVBA and others." in the AboutDialog.qml (/src/appshell/qml/AboutDialog.qml).

Greetings,
Gootector

Resolves: #NNNNN

• 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)

[Gootector]

Please squash all my commits and merge into the master. Thanks.

[cbjeukendrup]

Thanks!

[cbjeukendrup]

The failed check is probably because the branch of this PR is not up-to-date with other changes that have been made on the master branch in the meantime, but it doesn't matter. There is no way that this change can cause problems :)