Remove hipchat gem, and make HipChat service a no-op

What does this MR do?

The hipchat gem can no longer be used due to #325851 (closed)

Related issues

• #27954 (closed)
• #325851 (closed)
• gitlab-com/gl-infra/production#4054 (closed)

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

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