Bugfix: typescript not compiling, wrong type definition file.

Compiling any ts project that uses the agora-access-token module fails with

`TS1036: Statements are not allowed in ambient contexts.`

and

`TS2304: Cannot find name 'Role'`

Reason was a faulty index.d.ts. Seems like some copy-paste left overs.

DynamicKey/AgoraDynamicKey/nodejs/index.d.ts

@@ -86,7 +86,4 @@ export namespace RtmTokenBuilder {
      * @return token
      */
     export function buildToken(appID: string, appCertificate: string, account: string | number, role: number, privilegeExpiredTs: number): string;
-}
-
-module.exports.RtmTokenBuilder = RtmTokenBuilder
-module.exports.Role = Role
+}