[Discover] Clean up code to cancel Lens visualization changes when reverting saved search changes

[davismcphee]

In #175227 we added support for cancelling active Lens visualization changes when reverting saved search changes (via the unsaved changes badge) by manually accessing the cancel button in the DOM and programatically triggering a click. We're unsure of a better way to do this currently, but we should look into a more robust way of handling it:

kibana/src/plugins/discover/public/application/main/components/top_nav/get_top_nav_badges.tsx

Lines 49 to 52 in cfd69d7

	const lensEditFlyoutCancelButton = document.getElementById('lnsCancelEditOnFlyFlyout');
	if (lensEditFlyoutCancelButton) {
	lensEditFlyoutCancelButton.click?.();
	}

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)