Update our libraries to support php8.4

[wordpressfan]

Is your feature request related to a problem? Please describe.
Here #7220 we started adding the support of php8.4 in phpstan and fixed some deprecation errors related to:
https://php.watch/versions/8.4/implicitly-marking-parameter-type-nullable-deprecated

And we managed to update action scheduler to 3.9.1 which fixed all the deprecation errors from their side.

And I'm opening this issue as a follow-up to do the same with league container and mobile detect libraries.

Describe the solution you'd like
We'd need to check which version of those packages fix this error and discuss about this update and consequences.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[wordpressfan]

We faced a problem with action scheduler v3.9.1 so we reverted it to use v3.9 which still has some deprecation errors.

[webtrainingwheels]

https://secure.helpscout.net/conversation/2873133101/545436?viewId=377611
Implicitly marking parameter $callback as nullable is deprecated, the explicit nullable type must be used