Removes unnecessary source code

react/features/always-on-top/HangupButton.js

         api.executeCommand('hangup');
         window.close();
     }
-
-    /**
-     * Indicates whether this button is disabled or not.
-     *
-     * @override
-     * @private
-     * @returns {boolean}
-     */
-    _isDisabled() {
-        return false;
-    }
 }

react/features/invite/components/InviteButton.native.js

         }
     }
 
-    /**
-     * Indicates whether this button is disabled or not.
-     *
-     * @override
-     * @private
-     * @returns {boolean}
-     */
-    _isDisabled() {
-        return false;
-    }
-
     /**
      * Implements React's {@link Component#render()}.
      *

react/features/mobile/audio-mode/components/AudioRouteButton.js

         }
     }
 
-    /**
-     * Indicates whether this button is disabled or not.
-     *
-     * @override
-     * @private
-     * @returns {boolean}
-     */
-    _isDisabled() {
-        return false;
-    }
-
     _setVolumeComponent: (?Object) => void;
 
     /**

react/features/mobile/picture-in-picture/components/PictureInPictureButton.js

         this.props.dispatch(enterPictureInPicture());
     }
 
-    /**
-     * Indicates whether this button is disabled or not.
-     *
-     * @override
-     * @private
-     * @returns {boolean}
-     */
-    _isDisabled() {
-        return false;
-    }
-
     /**
      * Implements React's {@link Component#render()}.
      *

react/features/settings/components/web/SettingsButton.js

             dispatch(toggleSettings());
         }
     }
-
-    /**
-     * Indicates whether this button is disabled or not.
-     *
-     * @override
-     * @private
-     * @returns {boolean}
-     */
-    _isDisabled() {
-        return false;
-    }
 }
 
 /**

react/features/toolbox/components/AudioMuteButton.js

     label = 'toolbar.mute';
     tooltip = 'toolbar.mute';
 
-    /**
-     * Indicates if this button should be disabled or not.
-     *
-     * @override
-     * @private
-     * @returns {boolean}
-     */
-    _isDisabled() {
-        return false;
-    }
-
     /**
      * Indicates if audio is currently muted ot nor.
      *
         sendAnalytics(createToolbarEvent(AUDIO_MUTE, { enable: audioMuted }));
         this.props.dispatch(setAudioMuted(audioMuted));
     }
-
 }
 
 /**

react/features/toolbox/components/HangupButton.js

             this.props.dispatch(disconnect(true));
         }
     }
-
-    /**
-     * Indicates if this button should be disabled or not.
-     *
-     * @override
-     * @private
-     * @returns {boolean}
-     */
-    _isDisabled() {
-        return false;
-    }
 }
 
 export default translate(connect()(HangupButton));

react/features/toolbox/components/VideoMuteButton.js

                 VIDEO_MUTISM_AUTHORITY.USER,
                 /* ensureTrack */ true));
     }
-
 }
 
 /**

react/features/toolbox/components/native/AudioOnlyButton.js

         this.props.dispatch(toggleAudioOnly());
     }
 
-    /**
-     * Indicates whether this button is disabled or not.
-     *
-     * @override
-     * @private
-     * @returns {boolean}
-     */
-    _isDisabled() {
-        return false;
-    }
-
     /**
      * Indicates whether this button is in toggled state or not.
      *