[BUG] Metric explorer page time picker does not work

[venkateshamatam]

Description

The time picker on the 'metrics-explorer' page fails to update the metric names when a new time range is selected.

Steps to Reproduce

1. Navigate to the 'metrics-explorer' page at metrics-explorer.html.
2. Note that upon initial page load, an API call is made to /metric_names with a default time range of now-1h.
3. Change the time range using the time picker. Observe that no new API call is made to update the metric names for the selected time range, and the metric names dropdown remains unpopulated.

Expected Behavior

Upon selecting a new time range in the time picker, the metric names and other fields should update to reflect data over the new time range.