[lld] [llvm] [ELF] Rename IsRela to HasAddend (PR #96592)

[James Henderson via llvm-commits]

https://github.com/jh7370 approved this pull request.

LGTM, pending @smithp35's comments. (I note the buildkite failure, but assume it to be unrelated)

https://github.com/llvm/llvm-project/pull/96592