Fix failing spec/scripts/internal_events/cli_spec.rb test

What does this MR do and why?

spec/scripts/internal_events/cli_spec.rb attempts to look at a mocked TTY output to see if the CLI worked as behaved. However, the test started to fail because the output grew to 622 lines. However, the test looked only at the last 320 lines, but not all the expected outputs were contained in that window.

To fix this test, just look through the entire buffer instead of trying to limit by hundreds of rows.

Relates to #448636 (closed)

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How to set up and validate locally

bundle exec rspec ./spec/scripts/internal_events/cli_spec.rb:664