Corrected OpenSearchApi file name

Author: nhtruong

lib/Client.d.ts

@@ -10,7 +10,7 @@
 
 import { ConnectionOptions as TlsConnectionOptions } from 'tls';
 import { URL } from 'url';
-import OpenSearchAPI from '../api/OpenSearchAPI';
+import OpenSearchAPI from '../api/OpenSearchApi';
 import Serializer from './Serializer';
 import Helpers from './Helpers';
 import Connection, { AgentOptions, agentFn } from './Connection';

lib/Client.js

@@ -46,7 +46,7 @@ const kChild = Symbol('opensearchjs-child');
 const kExtensions = Symbol('opensearchjs-extensions');
 const kEventEmitter = Symbol('opensearchjs-event-emitter');
 
-const OpenSearchAPI = require('../api/OpenSearchAPI');
+const OpenSearchAPI = require('../api/OpenSearchApi');
 
 class Client extends OpenSearchAPI {
   constructor(opts = {}) {