[crater] Make summary sort order deterministic

Because these came from a hashmap and we then sorted only by the count,
if counts were equal the ordering could change between runs, which was
causing us to push a bunch of unnecessary commits.

fontc_crater/src/ci/html.rs

@@ -367,7 +367,7 @@ fn make_summary_report(current: &DiffResults) -> Markup {
         })
         .into_iter()
         .collect::<Vec<_>>();
-    results.sort_by_key(|(_, count)| -*count);
+    results.sort_by_key(|(item, count)| (-*count, *item));
 
     if results.is_empty() {
         return html!();