Deny a vacancy after it was deleted

[berkes]

When we delete a vacancy from the index, it might be re-indexed on a new run. In order to ensure a deleted vacancy never re-appears in the index, we should deny it somewhere.

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Acceptance criteria:

• Given a vacancy with the words "we are hiring" and uri "https://example.com/users/foo/statuses/1337" exists.
• When we call hunter2 --delete https://example.com/users/foo/statuses/1337
• And the status (vacancy) is still online
• And we then run the indexer
• Then we expect the vacancy "We are hiring" with uri "https://example.com/users/foo/statuses/1337" not to be in the index.