fix: Update enforce_mfa field to enforce_mfa_state (#601)

Signed-off-by: daeyeonko <kkdy21@naver.com>

Author: kkdy21

proto/spaceone/api/identity/v2/user.proto

@@ -161,7 +161,7 @@ message CreateUserRequest {
   // If reset_password is true, send email
   bool reset_password = 9;
   // +optional
-  optional bool enforce_mfa = 10;
+  string enforce_mfa_state = 10;
   // +optional
   string enforce_mfa_type = 11;
 
@@ -194,7 +194,7 @@ message UpdateUserRequest {
   // +optional
   bool reset_password = 8;
   // +optional
-  optional bool enforce_mfa = 9;
+  string enforce_mfa_state = 9;
   // +optional
   string enforce_mfa_type = 10;
 }