Update twilio/sdk To Version 8

[kellerjmrtn]

Unsure if this package is still being actively maintained, but twilio/sdk has released version 8. It may be worth bumping the dependency here to allow projects to update.

Oddly, the upgrade guide claims to not have breaking changes:

We ensured that you can upgrade to Php helper Library 8.0.0 version without any breaking changes of existing apis

However the changelog directly states otherwise

https://github.com/twilio/twilio-php/pull/803: Merge 8.0.0-rc into main. Thanks to @tiwarishubham635! (breaking change)

So I'm not sure what's going on there. Also potentially relevant #140