Lower dynamic picker debounce to 275ms

This seems a little bit low. Assuming words per minute are measured in
5 characters per word, typing very quickly at 80 WPM is 150ms per
character while a more average 40 WPM is 300ms. Since programming
symbols are involved we can assume that we drop down near ~35 WPM at
points where the debounce would need to be 350ms. So I think it makes
sense for this debounce to be somewhere in the 275-325ms range.

helix-term/src/ui/picker.rs

@@ -1219,7 +1219,7 @@ impl<T: 'static + Send + Sync, D: 'static + Send + Sync> AsyncHook for DynamicPi
         } else {
             self.query = Some(query);
 
-            Some(Instant::now() + Duration::from_millis(325))
+            Some(Instant::now() + Duration::from_millis(275))
         }
     }