Quarantine VirtualizationTest.ScrollToItem_AfterEndJump_LandsAtTarget

## Failing Test(s)

- `Microsoft.AspNetCore.Components.E2ETest.Tests.VirtualizationTest.ScrollToItem_AfterEndJump_LandsAtTarget`

This test is inherited (not overridden) by `Microsoft.AspNetCore.Components.E2ETest.ServerExecutionTests.ServerVirtualizationTest`, so quarantining the base method also covers that subclass instance.

## Failure data

Combined failures across `main`-branch CI (Source A) and merged-PR CI (Source B) over the past 30 days: **4 total failures** (2 from Source A, 2 from Source B).

The failure is a `Browser.Equal`/scroll-position timing assertion on the item scrolled to after an "end jump", consistent with intermittent flakiness (`is_consistent_regression: false` in the injected Source A data), not a code regression.

## Why quarantine

- Not currently quarantined (no `[QuarantinedTest]` attribute present).
- Never previously quarantined per `git log --follow -p -G 'QuarantinedTest'` history of this file.
- Not flagged as a consistent regression.
- Meets the ≥2-failure threshold for Case A quarantine, and repeats across both CI sources.

This issue tracks stabilizing the test before it can be unquarantined.

> Generated by [Daily Test Quarantine Management](https://github.com/dotnet/aspnetcore/actions/runs/32241253262) · auto · 341.3 AIC · ⌖ 10.4 AIC · ⊞ 4.2K · [◷](https://github.com/search?q=repo%3Adotnet%2Faspnetcore+is%3Aissue+%22gh-aw-workflow-call-id%3A+dotnet%2Faspnetcore%2Ftest-quarantine%22&type=issues)