Add proposer button is enabled for nested safe signers

[usame-algan]

Bug description

When connected with a wallet that is the owner of a nested safe the Add proposer button is enabled but it is not possible to add a proposer through a nested safe signature so the button needs to be disabled.

Steps to reproduce

1. Open a Safe A that has another Safe B as owner
2. Connect with a wallet that is an owner of Safe B
3. Go to the settings page

Expected result

The Add proposer button is enabled

Obtained result

The Add proposer should be disabled

[usame-algan]

Instead of adjusting the CheckWallet component I will create a new OnlyOwner component since we know that this button should only be available to owners and it reduces the scope and risk of breaking the behaviour a lot.