Auto merge of #23412 - servo:ssh, r=Manishearth

Add some SSH keys to tc-mac workers

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etc/taskcluster/macos/states/generic-worker.sls

@@ -6,6 +6,14 @@
 GMT:
   timezone.system
 
+sshkeys:
+  ssh_auth.present:
+    - user: root
+    - names:
+    {% for key in pillar["ssh_keys"] %}
+      - {{ key | yaml_encode }}
+    {% endfor %}
+
 {{ bin }}/generic-worker:
   file.managed:
     - name: