global-error-handler.md seems to unnecessary/outdated for Stimulus 3.x

[tmaier]

https://www.betterstimulus.com/error_handling/global-error-handler states an approach how to enable global error handling.

In 2021, following improvements landed in Stimulus: hotwired/stimulus#365

Based on this, the approach how to enable error handling, has been documented officially at https://stimulus.hotwired.dev/handbook/installing#error-handling. It states, that it supports window.onerror, which is being used by most error handlers, like Sentry.

This meas, the current approach is not really necessary anymore.