Increase required flit_core version to 3.11 (#5865)

Author: davidism

pyproject.toml

@@ -84,7 +84,7 @@ Chat = "https://discord.gg/pallets"
 flask = "flask.cli:main"
 
 [build-system]
-requires = ["flit_core<4"]
+requires = ["flit_core>=3.11,<4"]
 build-backend = "flit_core.buildapi"
 
 [tool.flit.module]