[Chapel Merge] Fix name of LLVM package for arch

Branch: refs/heads/main
Revision: cc1469727ca003cfa1e3b00fa7e78658c13d35d7
Author: benharsh
Link: Fix name of LLVM package for arch by benharsh · Pull Request #28827 · chapel-lang/chapel · GitHub
Log Message:
Fix name of LLVM package for arch (#28827)

Aliases for "llvm22" and "clang22" don't exist yet since 22 is the
latest version.

[reviewed-by @arifthpe]

Compare: Comparing d0e1e8f26116645f0b24ac3a1a6450e8f45394de...c02ee9eeecd2032e6b49fbdf462c0ac0287b091e · chapel-lang/chapel · GitHub

Diff:
M util/devel/test/portability/apptainer/current/arch/image.def
A util/devel/test/portability/provision-scripts/pacman-llvm.sh
https://github.com/chapel-lang/chapel/pull/28827.diff