fix: update license on instances (#38)

Author: sakulstra

src/contracts/instances/ATokenInstance.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: MIT
+// SPDX-License-Identifier: BUSL-1.1
 pragma solidity ^0.8.0;
 
 import {AToken, IPool, IAaveIncentivesController, IInitializableAToken, Errors, VersionedInitializable} from '../protocol/tokenization/AToken.sol';

src/contracts/instances/L2PoolInstance.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: MIT
+// SPDX-License-Identifier: BUSL-1.1
 pragma solidity ^0.8.0;
 
 import {L2Pool} from '../protocol/pool/L2Pool.sol';

src/contracts/instances/PoolConfiguratorInstance.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: MIT
+// SPDX-License-Identifier: BUSL-1.1
 pragma solidity ^0.8.0;
 
 import {PoolConfigurator, IPoolAddressesProvider, IPool, VersionedInitializable} from '../protocol/pool/PoolConfigurator.sol';

src/contracts/instances/PoolInstance.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: MIT
+// SPDX-License-Identifier: BUSL-1.1
 pragma solidity ^0.8.0;
 
 import {Pool} from '../protocol/pool/Pool.sol';

src/contracts/instances/VariableDebtTokenInstance.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: MIT
+// SPDX-License-Identifier: BUSL-1.1
 pragma solidity ^0.8.0;
 
 import {VariableDebtToken, IPool, IInitializableDebtToken, VersionedInitializable, IAaveIncentivesController, Errors} from '../protocol/tokenization/VariableDebtToken.sol';