[llvm] [NFC]Update a ThinLTO test case (PR #117584)

[Mingming Liu via llvm-commits]

mingmingl-llvm wrote:

> Ah, I assume you are trying to simulate a ThinLTO distributed backend. 

Yes, this is exactly what `opt -passes=function-import` tries to simulate. 

> Add "-import-all-index" to your opt invocation. This will do what a ThinLTO distributed backend will do and blindly follow the importing decisions encoded in the sharded index file, rather than trying to recompute the import decisions. See for example the invocations in llvm/test/ThinLTO/X86/distributed_import.ll.
> 

Thanks!  I added `-import-all-index` and updated `distributed_indexes.ll`. I reverted the change to `import_callee_declaration.ll` in this PR as there isn't much to test in the IR (except that the `opt` command shouldn't crash, but `distributed_index.ll` does this already).

https://github.com/llvm/llvm-project/pull/117584