feat(external_api,devices) drop use of isDeviceListAvailable

It's always true.

modules/API/external/external_api.js

@@ -11,7 +11,6 @@ import {
     getAvailableDevices,
     getCurrentDevices,
     isDeviceChangeAvailable,
-    isDeviceListAvailable,
     isMultipleAudioInputSupported,
     setAudioInputDevice,
     setAudioOutputDevice,
@@ -989,10 +988,15 @@ export default class JitsiMeetExternalAPI extends EventEmitter {
      * Returns Promise that resolves with true if the device list is available
      * and with false if not.
      *
+     * @deprecated
+     *
      * @returns {Promise}
      */
     isDeviceListAvailable() {
-        return isDeviceListAvailable(this._transport);
+        console.warn('isDeviceListAvailable is deprecated and will be removed in the future. '
+                     + 'It always returns true');
+
+        return Promise.resolve(true);
     }
 
     /**

modules/API/external/functions.js

@@ -56,21 +56,6 @@ export function isDeviceChangeAvailable(transport, deviceType) {
     });
 }
 
-/**
- * Returns Promise that resolves with true if the device list is available
- * and with false if not.
- *
- * @param {Transport} transport - The @code{Transport} instance responsible for
- * the external communication.
- * @returns {Promise}
- */
-export function isDeviceListAvailable(transport) {
-    return transport.sendRequest({
-        type: 'devices',
-        name: 'isDeviceListAvailable'
-    });
-}
-
 /**
  * Returns Promise that resolves with true if multiple audio input is supported
  * and with false if not.