Fix linter error

Author: kiaking

src/types/vuex-orm.ts

@@ -8,17 +8,17 @@ declare module '@vuex-orm/core' {
     /**
      * The api client.
      */
-    export var axios: AxiosInstance | null
+    export let axios: AxiosInstance | null
 
     /**
      * The global api configuration for all models.
      */
-    export var globalApiConfig: GlobalConfig
+    export let globalApiConfig: GlobalConfig
 
     /**
      * The api configuration for the model.
      */
-    export var apiConfig: Config | null
+    export let apiConfig: Config | null
 
     /**
      * Set the given axios instance.

test/feature/VuexORMAxios.spec.ts

@@ -20,6 +20,7 @@ describe('Feature - Vuex ORM Axios', () => {
   it('throws when calling api request without registering the axios', () => {
     VuexORM.use(VuexORMAxios)
 
+    // tslint:disable-next-line
     expect(() => { Model.api().axios }).toThrowError('Vuex ORM Axios')
   })
 })