fix(turborepo): Persistent tasks in watch mode (#8107)

### Description

Fixing persistent tasks in watch mode. I accidentally reversed the
dependency relation which created a circular dependency which in turn
caused a deadlock.

### Testing Instructions

Try out `turbo watch dev` in create turbo

Closes TURBO-3020

crates/turborepo-lib/src/engine/mod.rs

@@ -297,7 +297,7 @@ impl Engine<Built> {
                 continue;
             }
 
-            new_graph.add_edge(root_index, index, ());
+            new_graph.add_edge(index, root_index, ());
         }
 
         let task_lookup: HashMap<_, _> = new_graph