uudoc: Move tldr warning to README.md #15938

Job	Run time
Pre-commit hooks	41s
Style/spelling (ubuntu-latest, feat_os_unix)	14s
Style/lint (ubuntu-latest, all, true)	2m 15s
Style/Python	5s
Style/lint (macos-latest, feat_os_macos)	3m 20s
Style/toml	12s
Style/format (ubuntu-latest, feat_os_unix)	20s
Style/lint (windows-latest, feat_os_windows)	3m 25s
	10m 32s

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