Revert "[StackColoring] Delete dead stack slots (#75351)" (#75655)

This reverts commit 08b306dc.

it causes the following assertion failure:
llvm/include/llvm/CodeGen/MachineFrameInfo.h:530: int64_t
llvm::MachineFrameInfo::getObjectOffset(int) const: Assertion
`!isDeadObjectIndex(ObjectIdx) && "Getting frame offset for a dead
object?"' failed.