minor #5706 Update assetic.rst (Acinonux)

This PR was submitted for the 2.7 branch but it was merged into the 2.3 branch instead (closes #5706).

Discussion
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Update assetic.rst

assetic config fix

Commits
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c6616d1 Update assetic.rst

Author: xabbuh

reference/configuration/assetic.rst

@@ -58,8 +58,8 @@ Full Default Configuration
         <assetic:config
             debug="%kernel.debug%"
             use-controller="%kernel.debug%"
-            read-from="%kernel.root_dir%/../web"
-            write-to="%assetic.read_from%"
+            read-from="%assetic.read_from%"
+            write-to="%kernel.root_dir%/../web"
             java="/usr/bin/java"
             node="/usr/bin/node"
             sass="/usr/bin/sass"