Temporarily skip CloseUnrelatedProjectsInQ7Explorer due to upstream Eclipse Platform regression

[Copilot]

A recent Eclipse Platform UI change introduced a transient regression affecting Close Unrelated Project enablement, causing CloseUnrelatedProjectsInQ7Explorer to fail. This PR marks the test as temporarily skipped and documents the exact upstream reference and re-enable condition.

• Test metadata update

  • Added skipExecution to CloseUnrelatedProjectsInQ7Explorer.test tags so the failing scenario is excluded from execution while upstream behavior is unstable.

• Traceability in test description

  • Added a description note linking the upstream regression discussion:
    https://github.com/eclipse-platform/eclipse.platform.ui/pull/3871#issuecomment-4336933994
  • Added explicit guidance to re-enable once the Eclipse Platform fix reaches the staging repository.

• Change excerpt

  Tags: Q7Explorer, Project, skipExecution
  
  Note: skipExecution because of https://github.com/eclipse-platform/eclipse.platform.ui/pull/3871#issuecomment-4336933994.
  Re-enable this test after the Eclipse Platform fix (reverting this regression) reaches the staging repository.