Fix: Properly await `agent.run()` in README `Hello World` example (#5… #3359

Job	Run time
format	59s
lint	46s
codecov (./packages/autogen-core)	59s
codecov (./packages/autogen-magentic-one)	1m 57s
mypy (./packages/autogen-core)	2m 8s
codecov (./packages/autogen-ext)	2m 35s
pyright (./packages/autogen-core)	52s
mypy (./packages/autogen-magentic-one)	1m 3s
codecov (./packages/autogen-agentchat)	1m 6s
test (./packages/autogen-core)	57s
pyright (./packages/autogen-magentic-one)	59s
mypy (./packages/agbench)	1m 4s
pyright (./packages/agbench)	1m 4s
test (./packages/autogen-magentic-one)	1m 24s
mypy (./packages/autogen-ext)	2m 27s
test (./packages/autogen-ext)	2m 51s
mypy (./packages/autogen-agentchat)	1m 16s
test (./packages/autogen-agentchat)	1m 18s
mypy (./packages/magentic-one-cli)	1m 8s
pyright (./packages/autogen-ext)	1m 7s
pyright (./packages/autogen-agentchat)	55s
check-proto-changes-python	1m 5s
pyright (./packages/magentic-one-cli)	55s
docs (./packages/autogen-core)	1m 34s
docs-example-check (./packages/autogen-core)	2m 28s
markdown-code-lint	1m 53s
samples-code-check	52s
	37m 42s

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