Close updatenotification channel selector on click outside

While the vue-click-outside package was set up and
imported, it wasn't being used yet.

This commit sets up to use vue-click-outside
on the channel selector in updatenotification

Signed-off-by: Gary Kim <gary@garykim.dev>

apps/updatenotification/src/components/UpdateNotification.vue

@@ -77,7 +77,7 @@
 
 		<h3 class="update-channel-selector">
 			{{ t('updatenotification', 'Update channel:') }}
-			<div class="update-menu">
+			<div v-click-outside="closeUpdateChannelMenu" class="update-menu">
 				<span class="icon-update-menu" @click="toggleUpdateChannelMenu">
 					{{ localizedChannelName }}
 					<span class="icon-triangle-s" />
@@ -419,6 +419,9 @@ export default {
 		toggleMenu: function() {
 			this.openedWhatsNew = !this.openedWhatsNew
 		},
+		closeUpdateChannelMenu: function() {
+			this.openedUpdateChannelMenu = false
+		},
 		hideMenu: function() {
 			this.openedWhatsNew = false
 		},