Move from Box/Spout to OpenSpout

[Skullbock]

Is your feature request related to a problem? Please describe.
Not really a problem. Just saw that spout is unmaintained, and the folks at Spatie moved to its forked, mantained version openspout

Describe the solution you'd like
Simple change the dependency

Describe alternatives you've considered
None

Additional context
For reference, this is the commit in spatie/simple-excel

spatie/simple-excel@44ad112

[inxilpro]

Oh interesting. I'll take a look shortly!