Disable User System in front end config by default (#3228)

### Purpose:
Fix a mistake due to a misunderstanding. userSystemEnabled flag should
be set to false by default.

Co-authored-by: Texera <[email protected]>

Author: 2 people

core/gui/src/environments/environment.default.ts

@@ -26,7 +26,7 @@ export const defaultEnvironment = {
   /**
    * whether user system is enabled
    */
-  userSystemEnabled: true,
+  userSystemEnabled: false,
 
   /**
    * whether local login is enabled