chore(events,catalog/github): update docs from review comment

Signed-off-by: Rogerio Angeliski <angeliski@hotmail.com>

.changeset/old-bulldogs-fry.md

@@ -2,7 +2,7 @@
 '@backstage/plugin-catalog-backend-module-github': patch
 ---
 
-Handle Github `push` events at the `GithubEntityProvider` by subscribing to the topic `github.push.`
+Handle GitHub `push` events at the `GithubEntityProvider` by subscribing to the topic `github.push.`
 
 Implements `EventSubscriber` to receive events for the topic `github.push`.
 
@@ -10,7 +10,5 @@ On `github.push`, the affected repository will be refreshed.
 This includes adding new Location entities, refreshing existing ones,
 and removing obsolete ones.
 
-**Installation and Migration**
-
 Please find more information at
 https://backstage.io/docs/integrations/github/discovery#installation-with-events-support

docs/integrations/github/discovery.md

@@ -69,7 +69,6 @@ Set up your provider
 
 ```diff
 // packages/backend/src/plugins/catalogEventBasedProviders.ts
-+import { CatalogClient } from '@backstage/catalog-client';
 +import { GithubEntityProvider } from '@backstage/plugin-catalog-backend-module-github';
  import { EntityProvider } from '@backstage/plugin-catalog-node';
  import { EventSubscriber } from '@backstage/plugin-events-node';
@@ -98,6 +97,8 @@ Set up your provider
  }
 ```
 
+You can check the official docs to [configure your webhook](https://docs.github.com/en/developers/webhooks-and-events/webhooks/creating-webhooks) and to [secure your request]https://docs.github.com/en/developers/webhooks-and-events/webhooks/securing-your-webhooks()
+
 ## Configuration
 
 To use the discovery provider, you'll need a GitHub integration

plugins/catalog-backend-module-github/src/providers/GithubEntityProvider.ts

@@ -53,7 +53,7 @@ type Repository = {
   url: string;
   isArchived: boolean;
   repositoryTopics: string[];
-  defaultBranchRef: string | null;
+  defaultBranchRef?: string;
   isCatalogInfoFilePresent: boolean;
 };
 
@@ -213,7 +213,7 @@ export class GithubEntityProvider implements EntityProvider, EventSubscriber {
       return {
         url: r.url,
         name: r.name,
-        defaultBranchRef: r.defaultBranchRef?.name || null,
+        defaultBranchRef: r.defaultBranchRef?.name,
         repositoryTopics: r.repositoryTopics.nodes.map(t => t.topic.name),
         isArchived: r.isArchived,
         isCatalogInfoFilePresent: