fix: Remove unused BorrowerOperations from StabilityPool

contracts/src/Interfaces/IStabilityPool.sol

@@ -4,7 +4,6 @@ pragma solidity ^0.8.0;
 
 import "./IActivePool.sol";
 import "./ILiquityBase.sol";
-import "./IBorrowerOperations.sol";
 import "./IBoldToken.sol";
 import "./ITroveManager.sol";
 import "./IBoldRewardsReceiver.sol";
@@ -30,7 +29,6 @@ import "./IBoldRewardsReceiver.sol";
  *
 */
 interface IStabilityPool is ILiquityBase, IBoldRewardsReceiver {
-    function borrowerOperations() external view returns (IBorrowerOperations);
     function boldToken() external view returns (IBoldToken);
     function troveManager() external view returns (ITroveManager);
 

contracts/src/Interfaces/ITroveManager.sol

@@ -4,6 +4,7 @@ pragma solidity ^0.8.0;
 
 import "./ILiquityBase.sol";
 import "./ITroveNFT.sol";
+import "./IBorrowerOperations.sol";
 import "./IStabilityPool.sol";
 import "./IBoldToken.sol";
 import "./ISortedTroves.sol";

contracts/src/StabilityPool.sol

@@ -6,9 +6,7 @@ import "openzeppelin-contracts/contracts/token/ERC20/utils/SafeERC20.sol";
 
 import "./Interfaces/IStabilityPool.sol";
 import "./Interfaces/IAddressesRegistry.sol";
-import "./Interfaces/IBorrowerOperations.sol";
 import "./Interfaces/IStabilityPoolEvents.sol";
-import "./Interfaces/IBorrowerOperations.sol";
 import "./Interfaces/ITroveManager.sol";
 import "./Interfaces/IBoldToken.sol";
 import "./Interfaces/ISortedTroves.sol";
@@ -136,7 +134,6 @@ contract StabilityPool is LiquityBase, IStabilityPool, IStabilityPoolEvents {
     string public constant NAME = "StabilityPool";
 
     IERC20 public immutable collToken;
-    IBorrowerOperations public immutable borrowerOperations;
     ITroveManager public immutable troveManager;
     IBoldToken public immutable boldToken;
     // Needed to check if there are pending liquidations
@@ -206,25 +203,19 @@ contract StabilityPool is LiquityBase, IStabilityPool, IStabilityPoolEvents {
 
     // --- Events ---
 
-    event BorrowerOperationsAddressChanged(address _newBorrowerOperationsAddress);
     event TroveManagerAddressChanged(address _newTroveManagerAddress);
     event BoldTokenAddressChanged(address _newBoldTokenAddress);
     event SortedTrovesAddressChanged(address _newSortedTrovesAddress);
 
     constructor(IAddressesRegistry _addressesRegistry) LiquityBase(_addressesRegistry) {
         collToken = _addressesRegistry.collToken();
-        borrowerOperations = _addressesRegistry.borrowerOperations();
         troveManager = _addressesRegistry.troveManager();
         boldToken = _addressesRegistry.boldToken();
         sortedTroves = _addressesRegistry.sortedTroves();
 
-        emit BorrowerOperationsAddressChanged(address(borrowerOperations));
         emit TroveManagerAddressChanged(address(troveManager));
         emit BoldTokenAddressChanged(address(boldToken));
         emit SortedTrovesAddressChanged(address(sortedTroves));
-
-        // Allow funds movements between Liquity contracts
-        collToken.approve(address(borrowerOperations), type(uint256).max);
     }
 
     // --- Getters for public variables. Required by IPool interface ---

contracts/src/test/deployment.t.sol

@@ -110,12 +110,6 @@ contract Deployment is DevTestSetup {
         assertEq(activePoolAddress, recordedActivePoolAddress);
     }
 
-    function testStabilityPoolHasCorrectCorrectBorrowerOpsAddress() public view {
-        address borrowerOperationsAddress = address(borrowerOperations);
-        address recordedBorrowerOperationsAddress = address(stabilityPool.borrowerOperations());
-        assertEq(borrowerOperationsAddress, recordedBorrowerOperationsAddress);
-    }
-
     function testStabilityPoolHasCorrectCorrectBoldTokenAddress() public view {
         address boldTokenAddress = address(boldToken);
         address recordedBoldTokenAddress = address(stabilityPool.boldToken());