Saw a FIXME comment and decided to fix it.

This renames `descend_into_macros` to  `descend_into_macros_single` and `descend_into_macros_many` into `descend_into_macros`.
 However, this does not touch a function in `SemanticsImpl` of same name.

crates/ide/src/goto_implementation.rs

@@ -35,7 +35,7 @@ pub(crate) fn goto_implementation(
         })?;
     let range = original_token.text_range();
     let navs =
-        sema.descend_into_macros_many(original_token)
+        sema.descend_into_macros(original_token)
             .into_iter()
             .filter_map(|token| token.parent().and_then(ast::NameLike::cast))
             .filter_map(|node| {