Remove a few more explicit alloc:: and core::.

These were accidently re-introduced by
d645902620 after
39e57e3e9a landed.

crates/debug/src/write_debuginfo.rs

@@ -2,7 +2,6 @@ use faerie::artifact::{Decl, SectionKind};
 use faerie::*;
 use gimli::write::{Address, Dwarf, EndianVec, Result, Sections, Writer};
 use gimli::{RunTimeEndian, SectionId};
-use std::result;
 
 #[derive(Clone)]
 struct DebugReloc {