change deprecated sumBy() to sumOf()

[parneet-guraya]

Changed Deprecated function sumBy() with sumOf()

Android Studio Warning -> sumBy((T) -> Int): Int' is deprecated. Use sumOf instead

For -> AlbumsActivity It calculates the sum of the duration of the tracks of all the albums of a particular artist.

• [x] It is producing correct results.

For -> TracksActivity It calculates the sum of all the tracks present in a particular album.

• [x] It is producing correct result.

[parneet-guraya]

@tibbi Hi, can you review it? Thanks!

[tibbi]

will do it once I work on this app, thanks

[tibbi]

seems ok, thanks