[llvm] ELFRelocs/AArch64: update canonical reference URL (NFC) (PR #86955)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> Looks reasonable as for me, but I want to see other opinions on this. AFAIK, @smithp35 will be available next week.
> 
> Also, please do not override old history via force-pushes. While the PR is pretty trivial, it's still nice to see history of the changes.

The update looks good me, but the official sign-off should probably be from an ABI maintainer like @smithp35 

https://github.com/llvm/llvm-project/pull/86955