Update Salt repository on Debian

Summary:
Salt repository information has been updated for 3006+.

Reference: https://docs.saltproject.io/salt/install-guide/en/latest/topics/install-by-operating-system/debian.html

Fixes T1994.

Test Plan: Deploy on Eglide

Reviewers: DorianWinty

Reviewed By: DorianWinty

Maniphest Tasks: T1994

Differential Revision: https://devcentral.nasqueron.org/D3393