[desktop] Disable generate UUID button when editing user (#3428)

Forgot to disable this. Will be re-enabled when UUID changing can become
a thing

Signed-off-by: crueter <crueter@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3428
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

src/yuzu/configuration/system/new_user_dialog.cpp

@@ -86,6 +86,8 @@ void NewUserDialog::setup(Common::UUID uuid, const std::string& username, const
         ui->uuid->setReadOnly(true);
     }
 
+    ui->generate->setDisabled(m_editing);
+
     ui->username->setText(QString::fromStdString(username));
     verifyUser();