fix: use serve instead of app in task sequence (superlinear-ai#279)

Co-authored-by: Simon Palstermans <simon.palstermans@hotmail.be>

Author: sipalstermans

template/pyproject.toml.jinja

@@ -199,7 +199,7 @@ package = true
   [tool.poe.tasks.serve]
   help = "Serve the app"
 
-    [[tool.poe.tasks.app.sequence]]
+    [[tool.poe.tasks.serve.sequence]]
     cmd = "echo 'Serving app (placeholder)...'"
 {%- endif %}