[llvm] ci: Fix `pr-code-format` permissions for private forks (PR #120838)

[via llvm-commits]

whisperity wrote:

> Also, running the LLVM workflows in forks is not really a well-supported use case currently.
> 
> People hacking on the actions typically make sure they work in the monorepo at head and leave it at that.

In that case, should I create a patch that restricts the running of the action `if: github.repository_owner == 'llvm'` like it is done for many of the other workflow files?

> If people want to maintain this and the changes are simple enough and don't impact how they operate in the monorepo

It is very unlikely that anything would be changed by such a change.

@tstellar Can you (or someone who has the rights) check how LLVM organisation is set up? Likely the write permission isn't needed in

> The comments are added by this workflow instead: https://github.com/llvm/llvm-project/blob/main/.github/workflows/issue-write.yml

either, because [the org is set to allow write rights implicitly](https://github.com/organizations/llvm/settings/actions)?
![image](https://github.com/user-attachments/assets/e4f45c0d-4f8c-4289-b504-e2cd3332a3b1)


https://github.com/llvm/llvm-project/pull/120838