ref(crons): Center placeholder timeline view (#53376)

static/app/views/monitors/components/overviewTimeline/index.tsx

@@ -98,7 +98,7 @@ export function OverviewTimeline({monitorList}: Props) {
         <TimelineRow key={monitor.id}>
           <MonitorDetails monitor={monitor} />
           {isLoading || !monitorStats ? (
-            <Placeholder />
+            <TimelinePlaceholder />
           ) : (
             <div>
               <CheckInTimeline
@@ -181,3 +181,7 @@ const TimelineWidthTracker = styled('div')`
   grid-row: 1;
   grid-column: 2;
 `;
+
+const TimelinePlaceholder = styled(Placeholder)`
+  align-self: center;
+`;