Update challenge_21.md

Author: shivaylamba

Challenges/challenge_21.md

@@ -12,6 +12,6 @@ Today we will be learning about Git Aliases! :). This is an amazing feature that
 
  - Go through the Git Alias documentation shared here
  - Create at least 2 alias for any git commands you feel is too long
- - Take a screenshot of the alias you created. hint run `git config --list`
+ - Take a screenshot of the alias you created. hint run `git config --get-regexp alias`
  - Take a screenshot of using your alias
  - Post these screenshot in the issue created in the prior challenges