Fix bug in CloudscrapeClient::Executions::Results#collection

[henrikholm89]

So the problem was basically this:

If you use define_method on self.class, you'll create the new method as an instance method on the 
whole class so it will be available as a method on all instances of the class.

You can read more here:
https://stackoverflow.com/questions/19368437/how-to-use-define-method-inside-initialize

[henrikholm89]

Fixes #14