remove unused Display impl

Author: QuietMisdreavus

src/librustdoc/passes/calculate_doc_coverage.rs

@@ -7,7 +7,6 @@ use syntax::attr;
 use syntax_pos::FileName;
 
 use std::collections::BTreeMap;
-use std::fmt;
 use std::ops;
 
 pub const CALCULATE_DOC_COVERAGE: Pass = Pass {
@@ -67,12 +66,6 @@ impl ops::AddAssign for ItemCount {
     }
 }
 
-impl fmt::Display for ItemCount {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}/{}", self.with_docs, self.total)
-    }
-}
-
 #[derive(Default)]
 struct CoverageCalculator {
     items: BTreeMap<FileName, ItemCount>,