tests/codegen/enum/enum-match.rs: accept negative range attribute
The test current fails when `rustc` is built with HEAD LLVM: https://buildkite.com/llvm-project/rust-llvm-integrate-prototype/builds/38097/steps/canvas?sid=0197c492-5661-4c42-8ae7-3d789e85c6ca
I suspect the change was caused by 545cdca488
``@rustbot`` label llvm-main