[clang] [clang-tools-extra] [clangd] Fix unknown doxygen command parsing in parameter documentation (PR #202121)

[Maksim Ivanov via cfe-commits]

emaxx-google wrote:

Is it correct that this will have performance impact for code completion? How big would the slowdown be, and if it's big can we avoid it?

https://github.com/llvm/llvm-project/pull/202121