Replace SoundNotificationsManager by framework's sound notification

[regisd]

The SoundNotificationsManager class is used to add a sound to notifications, as far as I can tell.

The platform already plays a notification when the notification is build with setSound.

Replacing SoundNotificationsManager by the framework sound:

• reduces code size, which is always good
• avoids manipulating the MediaPlayer (which can be quite tricky, and can cause issues on some devices)

[artem-zinnatullin]

I am okay with that, but MediaPlayer allows us setting volume of the sound and as far as I remember notification can break music playing on some devices (ROMs)

[artem-zinnatullin]

@ilya-murzinov cc

[ilya-murzinov]

@regisd, I have the same concerns.
You can try to do this change and test on your device(s) though.