[X86] Remove disabled miscompiling X86CondBrFolding pass

As briefly discussed in IRC with @craig.topper,
the pass is disabled basically since it's original introduction (nov 2018)
due to  known correctness issues (miscompilations),
and there hasn't been much work done to fix that.

While i won't promise that i will "fix" the pass,
i have looked at it previously, and i'm sure i won't try to fix it
if that requires actually fixing this existing code.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D84775