If your notification said the guardian "has stopped guarding your wallet" it means they no longer want to be your guardian. We would advise you to replace them with another guardian.
If your notification said the guardian "will be removed in <time>", and you didn't request the removal, you have 24 hours to review the change and prevent it, if you want.
To cancel the removal, you should lock your wallet. This will prevent the change from taking place.
You can lock your wallet with an existing guardian at https://security.argent.xyz/lock-wallet if you have default Argent guardian, hardware wallet or Metamask as your wallet guardians.
You can ask your friend/family guardian to lock the wallet for you in their Argent app > Profile > Security > Guardians > Who I protect tab.