Change visibility to internal

Change-Id: I0c787ef6e64a13e17a5c1cd80179282cdf0cbe0a

Author: Jaehwa-Noh

core/ui/src/main/kotlin/com/google/samples/apps/nowinandroid/core/ui/JankStatsExtensions.kt

@@ -35,7 +35,7 @@ import kotlinx.coroutines.CoroutineScope
  * @see PerformanceMetricsState.getHolderForHierarchy
  */
 @Composable
-fun rememberMetricsStateHolder(): Holder {
+internal fun rememberMetricsStateHolder(): Holder {
     val localView = LocalView.current
 
     return remember(localView) {