fix governor related issue reported by C4

[rayeaster]

address following issues related to Governor/RoleAuthority:

• Unable to obtain all user roles code-423n4/2023-10-badger-findings#86
• RolesAuthority: Incorrectly removing the function signature from the target. code-423n4/2023-10-badger-findings#244

[GalloDaSballo]

NVM - The Fix in this PR avoids the bug introduced by the recommended fix from C4

[GalloDaSballo]

Comments

• 86 is tied to how uint8.max was a possible role which was skipped
  The naive mitigation would have caused overflow
  The implemented one avoids it

• 244 is tied to always calling
  enabledFunctionSigsByTarget[target].remove(bytes32(functionSig));
  Which would signal the fact that the function is not enabled, a view issue mostly

That said, the change

            if (getRolesWithCapability[target][functionSig] == bytes32(0)) {
                enabledFunctionSigsByTarget[target].remove(bytes32(functionSig));
            }

Avoids removing the target unless the bitmap is zeroed out

[GalloDaSballo]

See my comments above