Fix bugs in sync test

This test wrongly asserted that `initialSyncLimit` would be used to make a filter
It is used only for the initial sync inline filter, and not in POST /filter

Author: t3chguy

spec/unit/matrix-client.spec.ts

@@ -427,7 +427,7 @@ describe("MatrixClient", function() {
                 }
             });
         });
-        await client.startClient();
+        await client.startClient({ filter });
         await syncPromise;
     });
 

src/sync.ts

@@ -102,7 +102,7 @@ const MSC2716_ROOM_VERSIONS = [
 function getFilterName(userId: string, suffix?: string): string {
     // scope this on the user ID because people may login on many accounts
     // and they all need to be stored!
-    return `FILTER_SYNC_${userId}` + suffix ? "_" + suffix : "";
+    return `FILTER_SYNC_${userId}` + (suffix ? "_" + suffix : "");
 }
 
 function debuglog(...params) {