fix(google-analytics): fix parameter types in the trackMetric method (#…

…1780)

* Fix parameter in the trackMetric method

In the trackMetric the first parameter is a number type;

* Update index.ts

src/@ionic-native/plugins/google-analytics/index.ts

@@ -102,15 +102,15 @@ export class GoogleAnalytics extends IonicNativePlugin {
 
   /**
    * Track custom metric
-   * @param key {string}
+   * @param key {number}
    * @param value {any}
    * @returns {Promise<any>}
    */
   @Cordova({
     successIndex: 2,
     errorIndex: 3
   })
-  trackMetric(key: string, value?: any): Promise<any> { return; }
+  trackMetric(key: number, value?: number): Promise<any> { return; }
 
   /**
    * Track a screen