Fix pinned tab not showing issue

At time addFrame is called, location isn't known which causes the check (which is removed by this commit) to only allow one pinned tab through (since url is undefined). The rest of the pinned tabs were dropped. This check is not needed.
Realistically, our sites map already has unique keys and we only need to check if the pinned site is unique when a new one is added (check is in app/browser/tabs).

Fixes #8190

Auditors: @bbondy

Test Plan:
1. Pin multiple sites
2. Exit
3. Re-launch and verify sites are still pinned

js/state/frameStateUtil.js

@@ -421,13 +421,6 @@ function addFrame (windowState, tabs, frameOpts, newKey, partitionNumber, active
   // Only add pin requests if it's not already added
   const isPinned = frameOpts.isPinned
   delete frameOpts.isPinned
-  if (isPinned) {
-    const alreadyPinnedFrameProps = frames.find((frame) =>
-      frame.get('pinnedLocation') === location && frame.get('partitionNumber') === partitionNumber)
-    if (alreadyPinnedFrameProps) {
-      return {}
-    }
-  }
 
   // TODO: longer term get rid of parentFrameKey completely instead of
   // calculating it here.