fixing auth-app api docs for creating token via impersonation API

Author: nirajacharya2

services/auth-app/README.md

@@ -113,7 +113,7 @@ To impersonate, the respective requests from the CLI commands above extend with
 Example:\
 A final create request would then look like:
 ```bash
-curl --request POST 'https://<your host:9200>/auth-app/tokens?expiry={value}?userName={value}' \
+curl --request POST 'https://<your host:9200>/auth-app/tokens?expiry={value}&userName={value}' \
      --header 'accept: application/json' \
      --header 'authorization: Bearer {token}'
 ```