fix: Soften solidity version of FlashLoanBase contracts (#861)

Author: miguelmtzinf

contracts/flashloan/base/FlashLoanReceiverBase.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: AGPL-3.0
-pragma solidity 0.8.10;
+pragma solidity ^0.8.10;
 
 import {IFlashLoanReceiver} from '../interfaces/IFlashLoanReceiver.sol';
 import {IPoolAddressesProvider} from '../../interfaces/IPoolAddressesProvider.sol';

contracts/flashloan/base/FlashLoanSimpleReceiverBase.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: AGPL-3.0
-pragma solidity 0.8.10;
+pragma solidity ^0.8.10;
 
 import {IFlashLoanSimpleReceiver} from '../interfaces/IFlashLoanSimpleReceiver.sol';
 import {IPoolAddressesProvider} from '../../interfaces/IPoolAddressesProvider.sol';