minor #777 [config][translator] use the new fallbacks option. (aitboudad)

This PR was merged into the 2.3 branch.

Discussion
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[config][translator] use the new fallbacks option.

Commits
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9f0d0a1 [config][translator] use the new fallbacks option.

Author: fabpot

app/config/config.yml

@@ -4,7 +4,7 @@ imports:
 
 framework:
     #esi:             ~
-    #translator:      { fallback: "%locale%" }
+    #translator:      { fallbacks: ["%locale%"] }
     secret:          "%secret%"
     router:
         resource: "%kernel.root_dir%/config/routing.yml"