Remove Invisible MapMarker

This patch removes the map marker from the adventures list item of the
main menu dropdown. It is not being rendered and given that all other
elements do not have an icon, it is probably a remnant of old code and
left by accident.

frontend/src/lib/components/Navbar.svelte

@@ -121,7 +121,6 @@
 			>
 				{#if data.user}
 					<li>
-						<MapMarker />
 						<button on:click={() => goto('/adventures')}>{$t('navbar.adventures')}</button>
 					</li>
 					<li>