Remove unused Cleanup method from AofDirectoryCreator

The Cleanup method was never called anywhere in the codebase. AOF test
files handle cleanup directly using os.RemoveAll in their teardown
functions registered via stageHarness.RegisterTeardownFunc.

Additionally, the stageHarness parameter in the method was unused, and
the method returned error unlike RDBFileCreator.Cleanup() which returns
nothing, creating an inconsistency.

This also removes the now-unused test_case_harness import.

Author: cursoragent

internal/aof_directory_creator.go

@@ -9,7 +9,6 @@ import (
 	encoder "github.com/codecrafters-io/redis-tester/internal/resp/encoder"
 	value "github.com/codecrafters-io/redis-tester/internal/resp/value"
 	"github.com/codecrafters-io/tester-utils/logger"
-	"github.com/codecrafters-io/tester-utils/test_case_harness"
 	"github.com/dustin/go-humanize/english"
 )
 
@@ -121,10 +120,6 @@ func (a *AofDirectoryCreator) createManifestFile(logger *logger.Logger, manifest
 	return nil
 }
 
-func (a *AofDirectoryCreator) Cleanup(stageHarness *test_case_harness.TestCaseHarness) error {
-	return os.RemoveAll(filepath.Join(a.DataDirectory, a.AppendDirName))
-}
-
 func (a *AofDirectoryCreator) verifyMemberValues() {
 	if a.DataDirectory == "" {
 		panic("Codecrafters Internal Error - DataDirectory cannot be empty in AofDirectoryCreator")