Bug 1726117 - Remove snapshot configuration for debian-packages tasks. r=taskgraph-reviewers,bhearsum

It hasn't been used since bug 1431523.

Differential Revision: https://phabricator.services.mozilla.com/D122828

taskcluster/ci/packages/debian.yml

@@ -6,7 +6,6 @@ job-defaults:
     run:
         using: debian-package
         dist: jessie
-        snapshot: 20210208T213147Z
 
 deb10-cmake:
     description: "Cmake backport for Debian buster"

taskcluster/taskgraph/transforms/job/distro_package.py

@@ -62,10 +62,6 @@ debian_schema = common_schema.extend(
         Required("using"): "debian-package",
         # Debian distribution
         Required("dist"): text_type,
-        # Date of the snapshot (from snapshot.debian.org) to use, in the format
-        # YYYYMMDDTHHMMSSZ. The same date is used for the base docker-image name
-        # (only the YYYYMMDD part).
-        Required("snapshot"): text_type,
     }
 )