bump scaffolded flask version to 3.0.0 (#4121)

Author: alexyaang

resources/templates/python/requirements.txt.template

@@ -7,7 +7,7 @@ fastapi[all]==0.89.0
 uvicorn[standard]==0.20.0
 {{/if}}
 {{#if (eq platform 'Python: Flask')}}
-flask==2.2.2
+flask==3.0.0
 {{/if}}
 {{#unless (eq platform 'Python: General')}}
 gunicorn==20.1.0