[llvm] llvm-ar `N` argument: re-add truncated sentence (PR #169977)

[James Henderson via llvm-commits]

https://github.com/jh7370 commented:

Looks good, except for a minor point: we normally flow our documentation to the same line length rules as our code, i.e. 80 columns. Please could you update the PR, so that each line in the paragraph is as long as possible without breaching that limit.

https://github.com/llvm/llvm-project/pull/169977