fix(extended-device-information): fix wrong decorator

DEVELOPER.md

@@ -194,7 +194,7 @@ Checks if the plugin and property exist before getting/setting the property's va
 
 Example:
 ```ts
-@CordovaProperty
+@CordovaProperty()
 someProperty: string;
 ```
 

src/@ionic-native/plugins/extended-device-information/index.ts

@@ -53,6 +53,6 @@ export class ExtendedDeviceInformation extends IonicNativePlugin {
   /**
    * Get the total storage
    */
-  @CordovaProperty
+  @CordovaProperty()
   freestorage: number;
 }