[llvm] [llvm-ar] --help: fix unquoted angle bracket (PR #101364)

[Linux User via llvm-commits]

LinuxUserGD wrote:

> In this case, < is intended to represent the "read stdin from file" indicator.


I've readded it now with a space, so I guess the syntax would be `[-M < mri-script]`

https://github.com/llvm/llvm-project/pull/101364