Bug 1675051 - run Linux DevEdition tests as the expected tier 1. r=jmaher DONTBUILD

The migration of the task images from Ubuntu 16.04 to Ubuntu 18.04 in
bug 1602863 added the Ubuntu version to the platform. The platform of Linux x64
DevEdition didn't get added and used the default tier 2. We don't run tests
for Linux 32-bit anymore.

Differential Revision: https://phabricator.services.mozilla.com/D95754

taskcluster/taskgraph/transforms/tests.py

@@ -903,6 +903,7 @@ def set_tier(config, tasks):
                 "linux1804-64/opt",
                 "linux1804-64/debug",
                 "linux1804-64-shippable/opt",
+                "linux1804-64-devedition/opt",
                 "linux1804-64-qr/opt",
                 "linux1804-64-qr/debug",
                 "linux1804-64-shippable-qr/opt",