Update lang publish path according to the Laravel 9 convention

[dandarie]

Fixes #108

[welcome[bot]]

BOOM! Your first PR with us, thank you so much! Someone will take a look at it shortly. Please keep in mind that:

• if this constitutes a breaking change, it might take quite a while for this to get merged; we try to emulate the Laravel release cycle as much as possible, so developers can upgrade both software once; this means a new big release every ~6 months;
• even if it's a non-breaking change, it might take a few days/weeks for the PR to get merged; unless it's a no-brainer, we like to have some community feedback on new features, before we merge them; this leads to higher-quality code, in the end; we learnt this the hard way :-)
• not all PRs get merged; sometimes we just have to hold out new features, to keep the packages lean; sometimes we don't include features that only apply to niche use cases;
• we're not perfect; if you think we're wrong, call us out on it; but in a kind way :-) we all make mistakes, best we learn from them and build better software together;

Thank you! -- Justin Case The Backpack Robot

[promatik]

Hi @dandarie! Thank you for your contribution, I just merged your commit in a bigger PR where we are refactoring a little bit this package. Since it's a big refactoring, to avoid future conflicts I merged it there, that way we keep the credits to you 🙌

You can see it there; https://github.com/Laravel-Backpack/BackupManager/pull/105/commits