[llvm] [BOLT][test] Disable PLT check in callcont-fallthru (PR #139953)

[Amir Ayupov via llvm-commits]

aaupov wrote:

> You may also inspect the `a at plt` output from `llvm-objdump -d`. I prefer it (as you can test additional useful stuff) even if llvm-nm implements `--synthetic`.

The problem is that the call to nm is inside a wrapper constructing the profile, and replacing nm with objdump is non-trivial.

https://github.com/llvm/llvm-project/pull/139953