Use titlecase for Product Playbook

We've avoided it elsewhere, but the Docusaurus router is case sensitive. This change will fix
urls to their old casing, so it won't break links for product/

Author: spikeheap

sidebars.js

@@ -18,7 +18,7 @@ const sidebars = {
   apiDevelopment: [{type: 'autogenerated', dirName: 'api-playbook'}],
   frontendDevelopment: [{type: 'autogenerated', dirName: 'frontend-development'}],
   apiSpecifications: [{type: 'autogenerated', dirName: 'api-specifications'}],
-  productPlaybook: [{type: 'autogenerated', dirName: 'product-playbook'}],
+  productPlaybook: [{type: 'autogenerated', dirName: 'Product-Playbook'}],
 };
 
 export default sidebars;

src/components/HomepageFeatures/index.js

@@ -52,7 +52,7 @@ const FeatureList = [
   },
   {
     title: 'Product Playbook',
-    linkTo: '/product-playbook',
+    linkTo: '/Product-Playbook',
     description: (
       <>
         Hackney's product strategy, and how the Product teams work