Remove shumphrey from core developers

[shumphrey]

I'm no longer active in the Perl community :(

I should have done this some time ago.

[veryrusty]

Thanks for your input and effort over the years @shumphrey! Hope your current tools of the trade bring you as much joy as Perl and Dancer have.

[cromedome]

Sorry to see you go, @shumphrey. Thanks for all you've contributed to our community, and I wish you the best on your future endeavors!

[bigpresh]

Echoing the sorry to see you go, @shumphrey, and thanks for your work over the years.