fix: routing path for cdk/testing

renames `test-harnesses` route to `testing` as entry point for `cdk/testing` is latter in packages repository, this was causing links to not work properly when redirected to a route with `test-harnesses`

src/app/shared/documentation-items/documentation-items.ts

@@ -530,7 +530,7 @@ const DOCS: { [key: string]: DocItem[] } = {
       },
     },
     {
-      id: 'test-harnesses',
+      id: 'testing',
       name: 'Component Harnesses',
       summary: 'Foundation for component test harnesses.',
       exampleSpecs: {