fix: correct RoleGranted event documentation for existing members (#6036)

Co-authored-by: Ernesto García <[email protected]>

Author: phrwlk

contracts/access/manager/IAccessManager.sol

@@ -36,7 +36,7 @@ interface IAccessManager {
      *
      * NOTE: The meaning of the `since` argument depends on the `newMember` argument.
      * If the role is granted to a new member, the `since` argument indicates when the account becomes a member of the role,
-     * otherwise it indicates the execution delay for this account and roleId is updated.
+     * otherwise it indicates the timestamp when the execution delay update takes effect for this account and roleId.
      */
     event RoleGranted(uint64 indexed roleId, address indexed account, uint32 delay, uint48 since, bool newMember);