Don't log extra background events (#5134)

src/lib/statsig/statsig.tsx

···
     let secondsActive = 0
     if (lastActive != null) {
       secondsActive = Math.round((performance.now() - lastActive) / 1e3)
+      lastActive = null
+      logEvent('state:background:sampled', {
+        secondsActive,
+      })
     }
-    lastActive = null
-    logEvent('state:background:sampled', {
-      secondsActive,
-    })
   }
 })