chore: remove unused import (#466)

**Motivation:**

`ServiceManagerBase` imported `LibMergeSort`

**Modifications:**

Remove unused import. 

**Result:**

Only used imports.

Author: ypatil12

src/ServiceManagerBase.sol

@@ -28,7 +28,6 @@ import {ISlashingRegistryCoordinator} from "./interfaces/ISlashingRegistryCoordi
 import {IStakeRegistry} from "./interfaces/IStakeRegistry.sol";
 
 import {BitmapUtils} from "./libraries/BitmapUtils.sol";
-import {LibMergeSort} from "./libraries/LibMergeSort.sol";
 
 /**
  * @title Minimal implementation of a ServiceManager-type contract.