Fix visual accessibility issues 6 and 20 #5173

Job	Run time
docs (./packages/autogen-core)	1m 41s
format	53s
lint	55s
mypy (./packages/autogen-core)	3m 33s
test (./packages/autogen-core)	1m 4s
pyright (./packages/autogen-core)	1m 0s
mypy (./packages/agbench)	1m 15s
test (./packages/autogen-ext)	4m 20s
test-grpc	1m 30s
pyright (./packages/agbench)	1m 7s
test (./packages/autogen-agentchat)	1m 13s
mypy (./packages/autogen-ext)	3m 4s
pyright (./packages/autogen-ext)	1m 11s
check-proto-changes-python	1m 32s
mypy (./packages/autogen-agentchat)	1m 28s
pyright (./packages/autogen-agentchat)	59s
mypy (./packages/magentic-one-cli)	1m 35s
pyright (./packages/magentic-one-cli)	1m 10s
docs-example-check (./packages/autogen-core)	3m 54s
markdown-code-lint	2m 51s
samples-code-check	1m 5s
codecov (./packages/autogen-core)	9s
codecov (./packages/autogen-ext)	9s
codecov (./packages/autogen-agentchat)	14s
codecov (autogen-ext-grpc)	8s
	38m 0s

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