Bug 1606869: Switch decision task docker caches to match the rest the in-tree caches; r=Callek

Differential Revision: https://phabricator.services.mozilla.com/D58638

--HG--
extra : moz-landing-system : lando

.taskcluster.yml

@@ -213,7 +213,7 @@ tasks:
                   ACTION_CALLBACK: '${action.cb_name}'
 
           cache:
-            level-${repository.level}-checkouts-sparse-v2: /builds/worker/checkouts
+            gecko-level-${repository.level}-checkouts-sparse-v2: /builds/worker/checkouts
 
           features:
             taskclusterProxy: true