fix: update kill test to use valid sandbox ID format (#1169)

The infra now validates sandbox ID format (^[a-z0-9]+$), allowing only
lowercase alphanumeric characters. The test was using
'non-existing-sandbox' which fails format validation due to hyphens,
returning a 400 error instead of reaching the expected 404 path.

This updates the test to use 'nonexistingsandbox' — a valid format that
doesn't exist, so it properly hits the 404 "not found" response and
returns false as expected.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk: test-only change that updates hardcoded IDs to match new
validation rules, without modifying runtime logic.
> 
> **Overview**
> Updates JS and Python SDK `kill non-existing sandbox` tests to use a
lowercase alphanumeric sandbox ID (`nonexistingsandbox`) instead of a
hyphenated one, so the tests exercise the intended *not-found* path
rather than failing format validation.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
e43acb6. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Jakub Novak <jakub@e2b.dev>

Author: dobrac

packages/js-sdk/tests/api/kill.test.ts

@@ -17,5 +17,5 @@ sandboxTest.skipIf(isDebug)(
 )
 
 sandboxTest.skipIf(isDebug)('kill non-existing sandbox', async () => {
-  await expect(Sandbox.kill('non-existing-sandbox')).resolves.toBe(false)
+  await expect(Sandbox.kill('nonexistingsandbox')).resolves.toBe(false)
 })

packages/python-sdk/tests/async/api_async/test_sbx_kill.py

@@ -18,4 +18,4 @@ async def test_kill_existing_sandbox(async_sandbox: AsyncSandbox, sandbox_test_i
 
 @pytest.mark.skip_debug()
 async def test_kill_non_existing_sandbox():
-    assert not await AsyncSandbox.kill("non-existing-sandbox")
+    assert not await AsyncSandbox.kill("nonexistingsandbox")

packages/python-sdk/tests/sync/api_sync/test_sbx_kill.py

@@ -18,4 +18,4 @@ def test_kill_existing_sandbox(sandbox: Sandbox, sandbox_test_id: str):
 
 @pytest.mark.skip_debug()
 def test_kill_non_existing_sandbox():
-    assert not Sandbox.kill("non-existing-sandbox")
+    assert not Sandbox.kill("nonexistingsandbox")