Fix bitrate value used for video transcoding (#5183)

* Fix bitrate value used for video transcoding:

It should be 1000 times what it is now. The video size estimation was wrong since the retrieved duration value was in milliseconds, not seconds.

* Use `Duration` as the result type for `getDuration`

libraries/androidutils/src/main/kotlin/io/element/android/libraries/androidutils/media/VideoCompressorHelper.kt

@@ -38,7 +38,7 @@ class VideoCompressorHelper(
         val pixelsPerFrame = outputSize.width * outputSize.height
         // Apparently, 0.1 bits per pixel is a sweet spot for video compression
         val bitsPerPixel = 0.1f
-        return (pixelsPerFrame * bitsPerPixel * frameRate).toLong() / 1000
+        return (pixelsPerFrame * bitsPerPixel * frameRate).toLong()
     }
 }