docs: improve

src/FixedRateIrm.sol

@@ -54,6 +54,7 @@ contract FixedRateIrm is IFixedRateIrm {
     }
 
     /// @inheritdoc IIrm
+    /// @dev Reverts on not set rate, so the rate has to be set before the market creation.
     function borrowRate(MarketParams memory marketParams, Market memory) external view returns (uint256) {
         uint256 borrowRateCached = _borrowRate[marketParams.id()];
         require(borrowRateCached != 0, RATE_NOT_SET);

src/interfaces/IFixedRateIrm.sol

@@ -10,6 +10,6 @@ import {Id} from "../../lib/morpho-blue/src/interfaces/IMorpho.sol";
 interface IFixedRateIrm is IIrm {
     /// @notice Sets the borrow rate for a market.
     /// @dev A rate can be set by anybody, but only once.
-    /// @dev The creator of a market with this IRM would typically batch the creation with the setting of the rate.
+    /// @dev The creator of a market with this IRM would typically batch setting of the rate with the market creation.
     function setBorrowRate(Id id, uint256 newBorrowRate) external;
 }