[clang] [clang-format][docs] Clarify AllowShortFunctionsOnASingleLine deprecation (PR #195491)

[Björn Schäpers via cfe-commits]

https://github.com/HazardyKnusperkeks commented:

Better just remove the deprecated notice on the options. We will never remove that parsing and the example also contains it.

https://github.com/llvm/llvm-project/pull/195491