Update index.d.ts

Fix typo

Author: kaibolay

packages/firebase/compat/index.d.ts

@@ -1894,7 +1894,7 @@ declare namespace firebase.remoteConfig {
     settings: Settings;
 
     /**
-     * Object containing default values for conigs.
+     * Object containing default values for configs.
      */
     defaultConfig: { [key: string]: string | number | boolean };