Fix missed testTempDir(t) -> t.TempDir

tfexec/workspace_delete_test.go

diff --git a/tfexec/workspace_delete_test.go b/tfexec/workspace_delete_test.go
index 9dc90e2..1afa819 100644
--- a/tfexec/workspace_delete_test.go
+++ b/tfexec/workspace_delete_test.go
@@ -8,9 +8,7 @@
 )
 
 func TestWorkspaceDeleteCmd(t *testing.T) {
-	td := testTempDir(t)
-
-	tf, err := NewTerraform(td, tfVersion(t, testutil.Latest013))
+	tf, err := NewTerraform(t.TempDir(), tfVersion(t, testutil.Latest013))
 	if err != nil {
 		t.Fatal(err)
 	}