Update Dynamsoft_WebTwainEnv.md

Spelling correction on Download

Author: ogg25

info/api/Dynamsoft_WebTwainEnv.md

@@ -220,7 +220,7 @@ Check [license error list](https://www.dynamsoft.com/license-tracking/docs/commo
 
 ``` typescript
 /**
- * Update and downaload certificate (server.pem.ldsc & server_key.pem.ldsc) to DynamsoftServicex64_17\cert.
+ * Update and download certificate (server.pem.ldsc & server_key.pem.ldsc) to DynamsoftServicex64_17\cert.
  * @param url Url to download the new certificate. E.g. http://download.dynamsoft.com/cert.zip. server.pem.ldsc & server_key.pem.ldsc should be in cert.zip. 
  * @param successCallback A callback function that is executed if the request succeeds.
  * @param failureCallback A callback function that is executed if the request fails.