[lib] Deduplicate in getCandidateSidebarItemsForThreadList

Summary:
I made a mistake in D14154: I forgot to deduplicate the "general" and unread results.

Depends on D14157

Test Plan: Confirm I no longer see duplicated candidate sidebar items

Reviewers: varun, will

Reviewed By: varun

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D14158

lib/shared/sidebar-item-utils.js

@@ -167,10 +167,16 @@ async function getCandidateSidebarItemsForThreadList(
     topUnreadPromise,
   ]);
 
-  const topResults = [
-    ...topGeneralResults.slice(0, maxReadSidebars),
-    ...topUnreadResults.slice(0, maxUnreadSidebars),
-  ];
+  const topResults = topUnreadResults.slice(0, maxUnreadSidebars);
+  const topThreadIDs = new Set([
+    ...topResults.map(result => result.threadInfo.id),
+  ]);
+  const generalResults = topGeneralResults.slice(0, maxReadSidebars);
+  for (const result of generalResults) {
+    if (!topThreadIDs.has(result.threadInfo.id)) {
+      topResults.push(result);
+    }
+  }
 
   return topResults.map(result => {
     const {