Don't change text track mode back to `showing` about hls.js

[robwalch]

subtitleDisplay is a configuration option set at instantiation that determines how text tracks are handled. It should not be changed by action performed on tracks the media element.

The solution to the problem in the previous issue is to set subtitleDisplay to false. Changing the handling of track display and updating the config based on events from the tracks would reverse control and could break existing implementations of HLS.js.

[aradalvand]

subtitleDisplay = false actually seems to fix the issue. I didn't know that, I was under the impression that doing so would cause hls.js not to load the subtitles at all.
Alright then, thanks.