Fix Pages deletion modal title and accessible label

What does this MR do and why?

Use Delete Pages consistently for the modal title, button text, and accessible label.

• Root cause: shared confirmViaGlModal reads data-title and aria-label. The stale accessible label overrode the visible Delete Pages text.
• Scope: all three issues concern the same button, so one MR fixes them together.

Why “Delete Pages” is accurate

Deletion queues permanent removal of all Pages deployments. A new pipeline can redeploy the site; it does not undo deletion. See DeleteService lines 11–19 and DestroyDeploymentsService lines 5–13.

References

Resolves #629096 (closed)

Resolves #629097 (closed)

Resolves #629098 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Sign in as a Maintainer of a project with deployed Pages.
2. Go to Deploy > Pages, then Domains & settings.
3. Click Delete Pages to open the modal.
4. Verify the modal title, confirmation button, and accessible label read Delete Pages.
5. Click Cancel and verify the site remains available.
6. Repeat with vue3_migrate_pages enabled and disabled.
7. Optional: use a disposable test deployment to confirm deletion.

Validation passed:

• bundle exec rspec spec/features/projects/pages/user_edits_settings_spec.rb:189: 1 example passed. It failed before the fix because the expected heading was missing.
• Browser checks passed with vue3_migrate_pages on and off, including Cancel.
• Haml-lint, RuboCop, markdownlint-cli2, and Vale passed.
• Gettext extraction and lint passed.

MR acceptance checklist

Checked against the MR acceptance checklist:

• Tests, documentation, and translations verified.
• Changelog: fixed included.

CI: the branch push skipped CI. MR creation started a pipeline, which was canceled to leave the full run for a human to trigger.