Update mentee application status with revoke status

[anjula-sack]

Purpose

• The purpose of this PR is to fix Add a new mentee application status to handle revoked applications #147

Goals

• Adding a new state

Approach

• Update mentee application status with revoke status

Checklist

• This PR doesn't commit any keys, passwords, tokens, usernames, or other secrets.
• I have read and understood the development best practices guidelines ( http://bit.ly/sef-best-practices )
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation