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/channel/src/channel_store_tests.rs

@@ -343,7 +343,7 @@ fn init_test(cx: &mut AppContext) -> Model<ChannelStore> {
     release_channel::init(SemanticVersion::default(), cx);
     client::init_settings(cx);
 
-    let clock = Arc::new(FakeSystemClock::default());
+    let clock = Arc::new(FakeSystemClock::new());
     let http = FakeHttpClient::with_404_response();
     let client = Client::new(clock, http.clone(), cx);
     let user_store = cx.new_model(|cx| UserStore::new(client.clone(), cx));