No. You can't manually remove yourself from Premium Family subscription.
You need to reach out to the Family manager to get you removed from the plan.
I think this is how it goes:
1. *Request to get removed from the current Family manager.
2. Wait for your account to show as Spotify free. (spotify.com/accounts/subscription)
3. Ask for the invitation from new Family manager.
4. Complete the invitation.
*Note: If you can't get your manager to remove you from the plan, you can reach out to support. You can get in touch by going to this link:
https://support.spotify.com/us/contact-spotify-support/One more thing, this process only affects the account's subcription. Not the entire account. Meaning, you won't lose any playlist, music or anything.
Hope that helps!