autocomplete test: Tighten up "final results" test

The recent changes that added two new ranking criteria added four
new users to this test case.  Two is enough to make the test's point,
because it's enough for adding users that differ on the new criteria
while tying on the criteria that have higher priority in the ranking.

test/model/autocomplete_test.dart

@@ -705,8 +705,6 @@ void main() {
         eg.user(userId: 5, fullName: 'User Five'),
         eg.user(userId: 6, fullName: 'User Six', isBot: true),
         eg.user(userId: 7, fullName: 'User Seven'),
-        eg.user(userId: 8, fullName: 'User Xy', isBot: true),
-        eg.user(userId: 9, fullName: 'User Xz', isBot: true),
       ];
 
       await prepare(users: users, messages: [
@@ -723,19 +721,15 @@ void main() {
       // 1. Users most recent in the current topic/stream.
       // 2. Users most recent in the DM conversations.
       // 3. Human vs. Bot users (human users come first).
-      // 4. Alphabetical order.
+      // 4. Alphabetical order by name.
       check(await getResults(topicNarrow, MentionAutocompleteQuery('')))
-        .deepEquals([1, 5, 4, 2, 7, 3, 6, 8, 9]);
+        .deepEquals([1, 5, 4, 2, 7, 3, 6]);
 
       // Check the ranking applies also to results filtered by a query.
       check(await getResults(topicNarrow, MentionAutocompleteQuery('t')))
         .deepEquals([2, 3]);
       check(await getResults(topicNarrow, MentionAutocompleteQuery('f')))
         .deepEquals([5, 4]);
-      check(await getResults(topicNarrow, MentionAutocompleteQuery('s')))
-        .deepEquals([7, 6]);
-      check(await getResults(topicNarrow, MentionAutocompleteQuery('user x')))
-        .deepEquals([8, 9]);
     });
   });
 }