fix: DEP0044 in TerraformOutput (#2)

Don't use deprecated `util.isArray`.

This was originally approved as hashicorp/terraform-cdk#3861 but never
merged.

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### Related issue

Fixes hashicorp/terraform-cdk#3860 

### Description

When running on Node 22+, the following deprecation warning is logged:

> [DEP0044] DeprecationWarning: The util.isArray API is deprecated.
Please use Array.isArray() instead.

See https://nodejs.org/api/deprecations.html#DEP0044

There's no good reason to use `util.isArray`. It's an ancient API that's
been superseded by `Array.isArray()`. It's use here seems to be totally
unintentional, perhaps from bad autocomplete.

### Checklist

- [ ] I have updated the PR title to match [CDKTF's style
guide](https://github.com/open-constructs/cdk-terrain/blob/main/CONTRIBUTING.md#pull-requests-1)
- [ ] I have run the linter on my code locally
- [x] I have performed a self-review of my code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have made corresponding changes to the
[documentation](https://github.com/hashicorp/web-unified-docs/tree/main/content/terraform-cdk)
if applicable
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works if applicable
- [ ] New and existing unit tests pass locally with my changes

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Author: gabegorelick

packages/cdktn/lib/terraform-output.ts

@@ -5,7 +5,6 @@ import { TerraformElement } from "./terraform-element";
 import { deepMerge } from "./util";
 import { ITerraformDependable } from "./terraform-dependable";
 import { Expression } from ".";
-import { isArray } from "util";
 import { ITerraformAddressable } from "./terraform-addressable";
 import { Token } from "./tokens";
 import { Precondition } from "./terraform-conditions";
@@ -66,7 +65,7 @@ export class TerraformOutput extends TerraformElement {
     return (
       object &&
       typeof object === "object" &&
-      !isArray(object) &&
+      !Array.isArray(object) &&
       "fqn" in object
     );
   }