Remove race condition in test of splash page versioning

[AndrewKvalheim]

Checklist

• I have read the Contribution & Best practices Guide.
• My branch is up-to-date with the upstream master branch.
• The tests pass locally with my changes.
• I have added tests that prove my fix is effective or that my feature works (if appropriate).
• I have added necessary documentation (if appropriate).

Short description of what this resolves

A feature test currently fails intermittently due to a race condition in which the version history is viewed prior to the completion of a versioned change:

osem/spec/features/versions_spec.rb

Lines 251 to 255 in ae98ac1

	click_link 'Delete'
	page.accept_alert
	visit admin_revision_history_path
	expect(page).to have_text("#{organizer.name} created new splashpage with ID #{splashpage_id} in conference #{conference.short_title}")

$ rspec 'spec/features/versions_spec.rb:234'
…
Failures:

1) Version display changes in splashpages
    Failure/Error: expect(page).to have_text("#{organizer.name} created new splashpage with ID #{splashpage_id} in conference #{conference.short_title}")
    expected to find text "name50 created new splashpage with ID 1 in conference yvXgaw" in "…name50 created new splashpage in conference yvXgaw less than a minute ago…'

Note that the missing text "with ID" is rendered only for deleted items.

Changes proposed in this pull request

Wait for the change to complete.

[hennevogel]

This is in #2723 now, although disabled.