techdocs: fix tests by reusing the instantiated discovery

plugins/techdocs-backend/src/service/router.ts

@@ -26,10 +26,7 @@ import {
   PublisherBase,
   getLocationForEntity,
 } from '@backstage/techdocs-common';
-import {
-  PluginEndpointDiscovery,
-  SingleHostDiscovery,
-} from '@backstage/backend-common';
+import { PluginEndpointDiscovery } from '@backstage/backend-common';
 import { Entity } from '@backstage/catalog-model';
 import { getEntityNameFromUrlPath } from './helpers';
 import { DocsBuilder } from '../DocsBuilder';
@@ -105,10 +102,9 @@ export async function createRouter({
 
   router.get('/docs/:namespace/:kind/:name/*', async (req, res) => {
     const { kind, namespace, name } = req.params;
-    const discoveryApi = SingleHostDiscovery.fromConfig(config);
     const storageUrl =
       config.getOptionalString('techdocs.storageUrl') ??
-      `${await discoveryApi.getBaseUrl('techdocs')}/static/docs`;
+      `${await discovery.getBaseUrl('techdocs')}/static/docs`;
 
     const catalogUrl = await discovery.getBaseUrl('catalog');
     const triple = [kind, namespace, name].map(encodeURIComponent).join('/');