fix(FEC-14257): Fix duplicating captions on Safari (#806)

### Description of the Changes

Fixes issue on https://kaltura.atlassian.net/browse/FEC-14257

### CheckLists

- [ ] changes have been done against master branch, and PR does not
conflict
- [ ] new unit / functional tests have been added (whenever applicable)
- [ ] test are passing in local environment
- [ ] Travis tests are passing (or test results are not worse than on
master branch :))
- [ ] Docs have been updated

Co-authored-by: quantumInverter <[email protected]>

src/player.ts

@@ -2616,10 +2616,10 @@ export default class Player extends FakeEventTarget {
    * @returns {void}
    */
   private _updateTextDisplay(cues: Array<VTTCue>): void {
-    if (this._config.text.useShakaTextTrackDisplay) {
+    if (this._config.text.useShakaTextTrackDisplay && !(this._config.text.useNativeTextTrack || this._config.text.enableCEA708Captions)) {
       this._applyCustomSubtitleStyles();
     }
-    if (!this._config.text.useNativeTextTrack && !this._config.text.useShakaTextTrackDisplay) {
+    if (!this._config.text.useNativeTextTrack && !this._config.text.useShakaTextTrackDisplay && !this._config.text.enableCEA708Captions) {
       processCues(window, cues, this._textDisplayEl, this._textStyle);
     }
   }