Fix lint - Unsafe opt-in usage intended to be error-level severity

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

app/src/main/java/com/owncloud/android/ui/preview/PreviewMediaActivity.kt

@@ -390,6 +390,7 @@ class PreviewMediaActivity :
         }
     }
 
+    @OptIn(markerClass = [UnstableApi::class])
     private fun applyWindowInsets() {
         val playerView = binding.exoplayerView
         val exoControls = playerView.findViewById<FrameLayout>(R.id.exo_bottom_bar)