fix broken JSON

src/pages/_data/navigation/mainNav.json5

@@ -28,7 +28,7 @@
         { title: "Application Structure", url: "/build/application-structure/", children: [
           { title: "Zomes", url: "/build/zomes/", children: [
             { title: "Lifecycle Events and Callbacks", url: "/build/lifecycle-events-and-callbacks/" },
-            { title: "Zome Functions": url: "/build/zome-functions/" },
+            { title: "Zome Functions", url: "/build/zome-functions/" },
           ] },
         ]},
         { title: "Working with Data", url: "/build/working-with-data/", children: [