Modify comment.

engine/lib/phases/phase_rewrite_control_flow.mli

@@ -1,6 +1,6 @@
 (** This phase finds control flow expression (`if` or `match`) with a `return` expression
     in one of the branches. We replace them by replicating what comes after in all the branches. 
     This allows the `return` to be eliminated by `drop_needless_returns`.
-    This phase should come after phase_local_mutation. *)
+    This phase should come after `phase_local_mutation`. *)
 
 module Make : Phase_utils.UNCONSTRAINTED_MONOMORPHIC_PHASE