Drop --ignore-random-deprecation-check from markdown_cache rollout examples

What does this MR do and why?

Remove --ignore-random-deprecation-check from the markdown_cache rollout chatops command examples in the Banzai pipeline documentation.

References

• Permit --random with markdown_cache flags (gitlab-com/chatops!720 - merged) for the chatops MR which makes the argument no longer necessary.
• Add means to bump Markdown cache gradually (!236200 - merged) for the implementation of the FF, which necessitates the use of --random.

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