Fix one failure mode in the user guide #2326

Job	Run time
format	1m 18s
lint	58s
mypy (./packages/autogen-core)	2m 8s
pyright (./packages/autogen-core)	55s
pyright (./packages/autogen-magentic-one)	1m 5s
mypy (./packages/autogen-magentic-one)	1m 7s
pyright (./packages/agbench)	53s
pyright (./packages/autogen-ext)	58s
mypy (./packages/agbench)	1m 4s
pyright (./packages/autogen-agentchat)	1m 6s
mypy (./packages/autogen-ext)	1m 43s
check-proto-changes-python	1m 7s
mypy (./packages/autogen-agentchat)	1m 20s
docs (./packages/autogen-core)	1m 31s
docs-example-check (./packages/autogen-core)	2m 19s
test (./packages/autogen-core)	49s
test (./packages/autogen-magentic-one)	1m 33s
test (./packages/autogen-ext)	2m 35s
test (./packages/autogen-agentchat)	1m 2s
	25m 31s

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