debugging.md: Remove wrong claim that LLVM bitcode is not the same as LLVM IR

[Enselic]

They are the same thing since they can be converted back and forth without loss.

We hint at that in the second bullet point two paragraphs down:

• To get human readable versions of the LLVM bitcode, one just needs to convert
  the bitcode (.bc) files to .ll files using llvm-dis, which should be in
  the target local compilation of rustc.

That is also claimed in the last paragraph in this SO answer: https://stackoverflow.com/a/12954198/287761

[rustbot]

Thanks for the PR. If you have write access, feel free to merge this PR if it does not need reviews. You can request a review using r? rustc-dev-guide or r? <username>.

[rustbot]

⚠️ Warning ⚠️

• This PR is based on an upstream commit that is older than 7 days.

  It's recommended to update your branch according to the rustc-dev-guide.

[tshepang]

so, these are different formats of the same data, so I would not call them the same thing

your change still looks like an improvement though, other than the commit message

[Noratrieb]

"LLVM IR" is the abstract idea, bitcode being one way to format IR