updated copyright year

[firewave]

[danmar]

cli/cmdlineparser.h was changed in 2023 therefore we had 2023 as copyright year.

I don't have a strong opinion maybe we should just set to 2024 on all files. But then the release process should be adjusted. I update the copyright year on every release according to this instruction: https://github.com/danmar/cppcheck/blob/main/createrelease#L31

[firewave]

That looks reasonable. Closing.