fix(databases): vertically center backups sign up button

On the backups page for self-hosted, there's a button that takes users to Cloud since backups are not available on self-hosted. The button looked odd because it was aligned to the top. Instead, vertically center the button.

src/routes/(console)/project-[project]/databases/database-[database]/backups/upgradeCard.svelte

@@ -78,7 +78,7 @@
                     {/if}
                 </div>
             </div>
-            <div class="u-flex u-flex-vertical-mobile u-gap-mobile-6">
+            <div class="u-flex u-flex-vertical-mobile u-gap-mobile-6 u-cross-center">
                 <div class="u-flex-vertical u-gap-8">
                     <h3 class="body-text-2 u-bold">
                         {title}