docs: update CONTRIBUTING.md

[eltociear]

What kind of change does this PR introduce?

document fix

Other information:

Brabch -> Branch

[vercel]

@eltociear is attempting to deploy a commit to the Listinai Team on Vercel.

A member of the Team first needs to authorize it.

[Ikhlano]

Yeah i wanna work with you pls assign me
What changes are you trying to make to the CONTRIBUTING.md file?
Are you getting any error messages when you try to update the file?
Have you made any recent changes to your project or environment that might be causing the issue?

[jamesread]

Thanks for fixing the typo!