Fix group node tests teardown

[christian-byrne]

Tests added in #950 were unsuccessfully trying to reset state in individual test blocks. Moved teardown logic to afterEach.

[christian-byrne]

Model is not downloading in test env:

    Error: Timed out 5000ms waiting for expect(locator).toBeVisible()

    Locator: locator('.download-complete')
    Expected: visible
    Received: <element(s) not found>
    Call log:
      - expect.toBeVisible with timeout 5000ms
      - waiting for locator('.download-complete')


      102 |     // Wait for the element with the .download-complete selector to be visible
      103 |     const downloadComplete = comfyPage.page.locator('.download-complete')
    > 104 |     await expect(downloadComplete).toBeVisible()
          |                                    ^
      105 |   })
      106 | })
      107 |

        at /home/runner/work/ComfyUI_frontend/ComfyUI_frontend/ComfyUI_frontend/browser_tests/dialog.spec.ts:104:36

Works for me locally.

[huchenlei]

Failing tests are regressed by ComfyUI main repo's change.