chore: username is already unique and not-blank, so its enough to check

Author: ramazansakin

src/main/java/com/bezkoder/springjwt/controllers/AuthController.java

@@ -76,12 +76,6 @@ public ResponseEntity<?> registerUser(@Valid @RequestBody SignupRequest signUpRe
                     .body(new MessageResponse("Error: Username is already taken!"));
         }
 
-        if (userRepository.existsByEmail(signUpRequest.getEmail())) {
-            return ResponseEntity
-                    .badRequest()
-                    .body(new MessageResponse("Error: Email is already in use!"));
-        }
-
         // Create new user's account
         User user = new User(signUpRequest.getUsername(),
                 signUpRequest.getEmail(),