Use Instant not chrono for telemetry (#20756)

We occasionally see dates in the future appearing in our telemetry. One
hypothesis is that this is caused by a clock change while Zed is running
causing date math based on chrono to be incorrect.

Instant *should* be a more stable source of relative timestamps.

Release Notes:

- N/A

crates/semantic_index/examples/index.rs

@@ -25,7 +25,7 @@ fn main() {
             store.update_user_settings::<AllLanguageSettings>(cx, |_| {});
         });
 
-        let clock = Arc::new(FakeSystemClock::default());
+        let clock = Arc::new(FakeSystemClock::new());
 
         let http = Arc::new(HttpClientWithUrl::new(
             Arc::new(