[Video] Invert usage of `setAudioActive` (#4924)

src/App.native.tsx

···
 
   React.useEffect(() => {
     PlatformInfo.setAudioCategory(AudioCategory.Ambient)
-    PlatformInfo.setAudioActive(true)
+    PlatformInfo.setAudioActive(false)
     initPersistedState().then(() => setReady(true))
   }, [])
 

src/view/com/util/post-embeds/VideoEmbedInner/VideoEmbedInnerNative.tsx

···
         nativeControls={true}
         onEnterFullscreen={() => {
           PlatformInfo.setAudioCategory(AudioCategory.Playback)
-          PlatformInfo.setAudioActive(false)
+          PlatformInfo.setAudioActive(true)
           player.muted = false
         }}
         onExitFullscreen={() => {
           PlatformInfo.setAudioCategory(AudioCategory.Ambient)
-          PlatformInfo.setAudioActive(true)
+          PlatformInfo.setAudioActive(false)
           player.muted = true
           if (!player.playing) player.play()
         }}