Fix path resolution for child mods of those expanded by include!

[ObsidianMinor]

Child modules wouldn't use the correct candidate paths due to a branch that doesn't seem to be doing what it's intended to do. Removing the branch fixes the problem and all existing test cases pass.

Having no knowledge of how any of this works, I believe this fixes #17645. Using another test that writes the included mod directly into lib.rs instead, I found the difference can be traced to the candidate files we use to look up mods. A separate branch for if the file comes from an include! macro doesn't take into account the original mod we're contained within:

None if file_id.macro_file().map_or(false, |it| it.is_include_macro(db.upcast())) => {
    candidate_files.push(format!("{}.rs", name.display(db.upcast())));
    candidate_files.push(format!("{}/mod.rs", name.display(db.upcast())));
}

I'm not sure why this branch exists. Tracing the branch back takes us to 3bb9efb but it doesn't say why the branch was added. The test case that was added in this commit passes with the branch removed, so I think it's just superfluous at this point.

[Veykril]

That branch mightve gotten superceded by some recent changes to the include logic

[Veykril]

Thanks!
@bors r+

[bors]

📌 Commit b9469f5 has been approved by Veykril

It is now in the queue for this repository.

[bors]

⌛ Testing commit b9469f5 with merge 5f26438...

[bors]

☀️ Test successful - checks-actions
Approved by: Veykril
Pushing 5f26438 to master...