Fix a test flake involving zeroed out group_intervals (#20328)

Release Notes:

- N/A

crates/text/src/tests.rs

@@ -608,6 +608,7 @@ fn test_history() {
 fn test_finalize_last_transaction() {
     let now = Instant::now();
     let mut buffer = Buffer::new(0, BufferId::new(1).unwrap(), "123456".into());
+    buffer.history.group_interval = Duration::from_millis(1);
 
     buffer.start_transaction_at(now);
     buffer.edit([(2..4, "cd")]);

crates/text/src/text.rs

@@ -227,7 +227,7 @@ impl History {
         if let Some(mut entry) = entries.next_back() {
             while let Some(prev_entry) = entries.next_back() {
                 if !prev_entry.suppress_grouping
-                    && entry.first_edit_at - prev_entry.last_edit_at <= self.group_interval
+                    && entry.first_edit_at - prev_entry.last_edit_at < self.group_interval
                 {
                     entry = prev_entry;
                     count += 1;