[llvm] Revert "[AMDGPU][LTO] Assume closed world after linking (#105845)" (PR #106889)

[Shilei Tian via llvm-commits]

shiltian wrote:

Well, the assumption doesn't hold even w/ externally visible symbols in relocatable link. For example, if we read the callee from a global variable, that variable could be modified by other "dynamic library" to a function that is not visible in this module.

This needs either to be properly handled in `AAIndirectCallInfo`, or only to set the closed world bit when it is **really** a closed world.

https://github.com/llvm/llvm-project/pull/106889