[cleanup] While reading code.

Format per style apply_mutations.h

TEST=none

Change-Id: Ib47622068f46cb0c8c78cf59d72b199aaa6a42c7
diff --git a/bin/sessionmgr/story/model/apply_mutations.h b/bin/sessionmgr/story/model/apply_mutations.h
index e8a77ca..230392a 100644
--- a/bin/sessionmgr/story/model/apply_mutations.h
+++ b/bin/sessionmgr/story/model/apply_mutations.h
@@ -13,8 +13,8 @@
 // |current_model|.
 fuchsia::modular::storymodel::StoryModel ApplyMutations(
     const fuchsia::modular::storymodel::StoryModel& current_model,
-    const std::vector<fuchsia::modular::storymodel::StoryModelMutation>
-        &commands);
+    const std::vector<fuchsia::modular::storymodel::StoryModelMutation>&
+        commands);
 
 }  // namespace modular