Rollup merge of #106766 - GuillaumeGomez:rm-stripper-dead-code, r=notriddle

Remove dead code in rustdoc stripper

No changes when this code is removed.

cc `@aDotInTheVoid`
r? `@notriddle`

Author: Yuki Okushi

src/librustdoc/passes/stripper.rs

@@ -97,17 +97,7 @@ impl<'a, 'tcx> DocFolder for Stripper<'a, 'tcx> {
             }
 
             // handled in the `strip-priv-imports` pass
-            clean::ExternCrateItem { .. } => {}
-            clean::ImportItem(ref imp) => {
-                // Because json doesn't inline imports from private modules, we need to mark
-                // the imported item as retained so it's impls won't be stripped.
-                //
-                // FIXME: Is it necessary to check for json output here: See
-                // https://github.com/rust-lang/rust/pull/100325#discussion_r941495215
-                if let Some(did) = imp.source.did && self.is_json_output {
-                    self.retained.insert(did.into());
-                }
-            }
+            clean::ExternCrateItem { .. } | clean::ImportItem(_) => {}
 
             clean::ImplItem(..) => {}