Prepare Ribasim release v2024.9.0

[visr]

@HendrikKok give us a shout here if your coupling tests work ok on current main.

TeamCity builds are sometimes red, but this is https://github.com/JuliaLang/julia/issues/52272 causing unrelated trouble,

[Jingru923]

@visr Why in some file, the version number is still 2024.8.0 instead of 2024.9.0?

• changelog
• __init__.py under python/ribasim and python/ribasim_api
• metadata.txt

[visr]

Thanks, yes I missed some. The one in changelog shouldn't change since that describes the old release.