message: docs: update sign-in page example in getting started docs
diff: @@ -164,13 +164,6 @@ Open `packages/app/src/App.tsx` and below the last `import` line, add:
  ```typescript
  import { githubAuthApiRef } from '@backstage/core-plugin-api';
  import { SignInProviderConfig, SignInPage } from '@backstage/core-components';
  -
  -const githubProvider: SignInProviderConfig = {
  - id: 'github-auth-provider',
  - title: 'GitHub',
  - message: 'Sign in using GitHub',
  - apiRef: githubAuthApiRef,
  -};
  ```
  Search for `const app = createApp({` in this file, and below `apis,` add:
  @@ -181,7 +174,12 @@ components: {
  <SignInPage
  {...props}
  auto
  - provider={githubProvider}
  + provider={{
  + id: 'github-auth-provider',
  + title: 'GitHub',
  + message: 'Sign in using GitHub',
  + apiRef: githubAuthApiRef,
  + }}
  />
  ),
  },
  