fix(task-manager): fixed URL issues with handling editor and senior editor emails

While refactoring the sendMail mutation, we copied the previously written code. In this, the selectedEmail and externalEmail were redundant for the task notifications email flow. The selectedEmail was being used for setting the editor, reviewer flag. While we won't require externalEmail with scheduler functionality, because we are already processing recipient email through database. I have kept a single prop with scheduler using the send email mutation. It's working fine with all the editor roles now.