Update usage.rst

Typo?

Author: adpauly

workflow/usage.rst

@@ -229,7 +229,7 @@ order:
     * ``workflow.[workflow name].enter``
     * ``workflow.[workflow name].enter.[place name]``
 
-``work.flow.entered``
+``workflow.entered``
 
     Similar to ``workflow.enter``, except the marking store is updated before this
     event (making it a good place to flush data in Doctrine).