Fix .gitignore: stop tracking ignored files

backend/lib/openzeppelin-contracts/contracts/mocks/governance/GovernorCompMock.sol

@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../../governance/extensions/GovernorCountingSimple.sol";
+import "../../governance/extensions/GovernorVotesComp.sol";
+
+abstract contract GovernorCompMock is GovernorVotesComp, GovernorCountingSimple {
+    function quorum(uint256) public pure override returns (uint256) {
+        return 0;
+    }
+
+    function votingDelay() public pure override returns (uint256) {
+        return 4;
+    }
+
+    function votingPeriod() public pure override returns (uint256) {
+        return 16;
+    }
+}