fix two minor typos (#2755)

contracts/governance/README.adoc

@@ -3,7 +3,7 @@
 [.readme-notice]
 NOTE: This document is better viewed at https://docs.openzeppelin.com/contracts/api/governance
 
-This directory includes primitives for on-chain governance. We currently only offer the {TimelockController} contract, that can be used as a component in a governance systems to introduce a delay between a proposal and its execution.
+This directory includes primitives for on-chain governance. We currently only offer the {TimelockController} contract, that can be used as a component in a governance system to introduce a delay between a proposal and its execution.
 
 == Timelock
 

contracts/token/ERC20/extensions/ERC20VotesComp.sol

@@ -12,7 +12,7 @@ import "./ERC20Votes.sol";
  * with Governor Alpha or Bravo) and if you are sure the supply cap of 2^96^ is enough for you. Otherwise, use the
  * {ERC20Votes} variant of this module.
  *
- * This extensions keeps a history (checkpoints) of each account's vote power. Vote power can be delegated either
+ * This extension keeps a history (checkpoints) of each account's vote power. Vote power can be delegated either
  * by calling the {delegate} function directly, or by providing a signature to be used with {delegateBySig}. Voting
  * power can be queried through the public accessors {getCurrentVotes} and {getPriorVotes}.
  *