Remove check logic for file-tree-popover to avoid long wait

What does this MR do and why?

The file_tree_popover was introduced in Add file tree popover and save display state in... (!85874 - merged) and caused some failures as it would reappear under certain conditions -- therefore we added Dismiss the file tree popover if it block acces... (!87068 - merged) to dismiss the element if present.

With the fix in Dismiss file tree popover when clicking outside... (!88620 - merged) clicking outside the popover should permanently remove it so we can remove the extra check here that is adding extra waits in our suite that should not be required now.

How to set up and validate locally

cd /path/to/gdk/gitlab/qa 
bundle exec rspec qa/specs/features/browser_ui/4_verify/pipeline/pipeline_editor_tabs_spec.rb

MR acceptance checklist

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