Update links hash in main_navigation YAML

This changes it to match the labels in the contents_list component,
as well as the forthcoming side_navigation block.

Also removes links being hard-coded to active as this will be set my the
new helper.

lib/data/landing_page_content_items/landing_page.yaml

@@ -1,19 +1,15 @@
 blocks:
 - type: main_navigation
   links:
-  - label: Ipsums for Lorem
-    link: /ipsum
-    active: true
-  - label: Our Lorem
-    link: /our-lorem
-    active: false
+  - text: Ipsums for Lorem
+    href: /ipsum
+  - text: Our Lorem
+    href: /our-lorem
     children:
-      - label: Child 1
-        link: /a
-        active: false
-      - label: Child 2
-        link: /b
-        active: false
+      - text: Child 1
+        href: /a
+      - text: Child 2
+        href: /b
   title: Service name
   title_link: /landing-page
 - type: hero