Make 'suggestFix' method in 'SuggestionProvider' optional

Change 404399 introduced a required 'suggestFix' method, preventing
builds of existing SuggestionProvider implementations.

Google-Bug-Id: b/322003830
Release-Notes: skip
Change-Id: I12d1b9b4b6f7ecb0ac89335b5e37cc0ee4711349
diff --git a/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts b/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts
index c30646e..7f643a5 100644
--- a/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts
+++ b/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts
@@ -1093,7 +1093,7 @@
     const suggestionsProvider = this.suggestionsProvider;
     const changeInfo = this.getChangeModel().getChange();
     if (
-      !suggestionsProvider ||
+      !suggestionsProvider?.suggestCode ||
       !this.showGeneratedSuggestion() ||
       !changeInfo ||
       !this.comment ||