Update governor docs (#5420)

Author: arr00

contracts/governance/README.adoc

@@ -20,7 +20,7 @@ For a written walkthrough, check out our guide on xref:ROOT:governance.adoc[How
 
 Votes modules determine the source of voting power, and sometimes quorum number.
 
-* {GovernorVotes}: Extracts voting weight from an {ERC20Votes}, or since v4.5 an {ERC721Votes} token.
+* {GovernorVotes}: Extracts voting weight from an {IVotes} contract.
 
 * {GovernorVotesQuorumFraction}: Combines with `GovernorVotes` to set the quorum as a fraction of the total token supply.
 
@@ -30,7 +30,7 @@ Counting modules determine valid voting options.
 
 * {GovernorCountingFractional}: A more modular voting system that allows a user to vote with only part of its voting power, and to split that weight arbitrarily between the 3 different options (Against, For and Abstain).
 
-* {GovernorCountingOverridable}: An extended version of `GovernorCountingSimple` which allows delegatees to override their delegates while the vote is live.
+* {GovernorCountingOverridable}: An extended version of `GovernorCountingSimple` which allows delegatees to override their delegates while the vote is live. Must be used in conjunction with {VotesExtended}.
 
 Timelock extensions add a delay for governance decisions to be executed. The workflow is extended to require a `queue` step before execution. With these modules, proposals are executed by the external timelock contract, thus it is the timelock that has to hold the assets that are being governed.