removed default value form env

Author: shuhaib-aot

forms-flow-nav/src/constants/constants.js

@@ -204,5 +204,4 @@ export const IS_ENTERPRISE = window._env_?.REACT_APP_IS_ENTERPRISE || false;
 
 export const USER_NAME_DISPLAY_CLAIM =
    window._env_?.REACT_APP_USER_NAME_DISPLAY_CLAIM ||
-  process.env.REACT_APP_USER_NAME_DISPLAY_CLAIM ||
-  "preferred_username";
+  process.env.REACT_APP_USER_NAME_DISPLAY_CLAIM;