[llvm] [BOLT][test] Disable callcont-fallthru.s on AArch64 (PR #137831)

[Paschalis Mpeis via llvm-commits]

paschalis-mpeis wrote:

(continuing discussion to this PR)

Quoting @yota9 from [#135867 comment](https://github.com/llvm/llvm-project/pull/135867#issuecomment-2846852400):
> @paschalis-mpeis Indeed, you're right. Let's wait about @aaupov decision then, it LGTM

Great, thank you! @aaupov, are you happy hitting the green button here?

I've added a note to make sure we follow-up after #138232:
https://github.com/llvm/llvm-project/blob/751168add858177ccf3698cad9d10cf588513131/bolt/test/X86/callcont-fallthru.s#L4

https://github.com/llvm/llvm-project/pull/137831