test(studio): raise timeout for NewScopedTokenSheet tests (#51755)

## Summary

- The `NewScopedTokenSheet` tests were flaky on master. The 5s default
timeout was hit intermittently, most visibly in the "falls back to
Custom when a row diverges from the preset" test, plus some sibling
tests.
- Observed in unit-test runs on master. Reproduced locally by running
the file under heavy CPU load, where tests took 4.5-5s versus ~1s on an
idle machine.
- Fix: file-level `vi.setConfig({ testTimeout: 15_000 })`. This only
affects this file because vitest isolates test files.

## Testing

- Ran the file 5 times under the same CPU load. All 21 tests passed each
time.

apps/studio/components/interfaces/Account/AccessTokens/Scoped/NewScopedTokenSheet.test.tsx

@@ -25,6 +25,10 @@ vi.mock('common', async (importOriginal) => {
 const { mockTrack } = vi.hoisted(() => ({ mockTrack: vi.fn() }))
 vi.mock('@/lib/telemetry/track', () => ({ useTrack: () => mockTrack }))
 
+// Each test mounts the full sheet and walks several async steps. That takes ~1s on an idle
+// machine but approaches the default 5s limit when CI workers are saturated.
+vi.setConfig({ testTimeout: 15_000 })
+
 const user = userEvent.setup({
   writeToClipboard: true,
 })