fix: Flaky TestForDeps tests

The executor output for parallel task (and dep)
execution can come out one character at a time,
so even though the tests use `SyncWriter, the
writer's lock doesn't prevent interleaving.

Using `group` output forces the task output to be
buffered and kept together before being printed.

Fixes go-task#1819.

task_test.go

@@ -2489,6 +2489,8 @@ func TestForDeps(t *testing.T) {
 				Stderr: &buff,
 				Silent: true,
 				Force:  true,
+				// Force output of each dep to be grouped together to prevent interleaving
+				OutputStyle: ast.Output{Name: "group"},
 			}
 			require.NoError(t, e.Setup())
 			require.NoError(t, e.Run(context.Background(), &ast.Call{Task: test.name}))