feat(subtitles): Disable for guests.

react/features/subtitles/components/AbstractClosedCaptionButton.js

  */
 export function _abstractMapStateToProps(state: Object, ownProps: Object) {
     const { _requestingSubtitles } = state['features/subtitles'];
+    const { isGuest = true } = state['features/base/jwt'];
     const { transcribingEnabled } = state['features/base/config'];
-    const { visible = Boolean(transcribingEnabled) } = ownProps;
+    const { visible = Boolean(transcribingEnabled && !isGuest) } = ownProps;
 
     return {
         _requestingSubtitles,

react/features/subtitles/components/ClosedCaptionButton.native.js

  */
 export function mapStateToProps(state: Object, ownProps: Object) {
     const { transcribingEnabled } = state['features/base/config'];
-    const enabled = getFeatureFlag(state, CLOSE_CAPTIONS_ENABLED, true) && transcribingEnabled;
+    const { isGuest = true } = state['features/base/jwt'];
+    const enabled = getFeatureFlag(state, CLOSE_CAPTIONS_ENABLED, true) && transcribingEnabled && !isGuest;
     const { visible = enabled } = ownProps;
 
     return {