Remove generate-message-to-run-e2e-pipeline.rb script

What does this MR do and why?

This MR removes message introduced in !122896 (merged)

Some more work is required before we can re-introduce the message. Specifically, we need to figure out how to tie togeather trigger-omnibus, trigger-omnibus-env and e2e:package-and-test-ee jobs.

See this Slack thread (internal link) for details.

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