Add renouceAdmin function

[nmlinaric]

Description

Adds renouceAdmin function so we are able to change FeeHandlers admin

Related Issue Or Context

Closes: #584

How Has This Been Tested? Testing details.

Unit tests

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation

Checklist:

• I have commented my code, particularly in hard-to-understand areas.
• I have ensured that all acceptance criteria (or expected behavior) from issue are met
• I have updated the documentation locally and in chainbridge-docs.
• I have added tests to cover my changes.
• I have ensured that all the checks are passing and green, I've signed the CLA bot

[lastperson]

Why not calling grantRole, renounceRole directly?
Also if the grantRole is used inside a function, then there is no need to have onlyAdmin modifier.

[nmlinaric]

Why not calling grantRole, renounceRole directly? Also if the grantRole is used inside a function, then there is no need to have onlyAdmin modifier.

We wanted to make changing admin a one step process, either way someone could call directly call renounceRole before grantRole and lock themselves out of admin, but I think this way we make that a lesser chance.