Fix outdated docs about timelock admin (#3806)

docs/modules/ROOT/pages/governance.adoc

@@ -254,7 +254,7 @@ TimelockController uses an AccessControl setup that we need to understand in ord
 
 - The Proposer role is in charge of queueing operations: this is the role the Governor instance should be granted, and it should likely be the only proposer in the system.
 - The Executor role is in charge of executing already available operations: we can assign this role to the special zero address to allow anyone to execute (if operations can be particularly time sensitive, the Governor should be made Executor instead).
-- Lastly, there is the Admin role, which can grant and revoke the two previous roles: this is a very sensitive role that will be granted automatically to both deployer and timelock itself, but should be renounced by the deployer after setup.
+- Lastly, there is the Admin role, which can grant and revoke the two previous roles: this is a very sensitive role that will be granted automatically to the timelock itself, and optionally to a second account, which can be used for ease of setup but should promptly renounce the role.
 
 == Proposal Lifecycle