message: docs(auth): align provider reference with config example
  The used provider reference was not aligned with the config example.
diff: @@ -89,7 +89,7 @@ credentials fresh.
  When using the OAuth2-Proxy, the Backstage UI can only be accessed after the
  user has already been authenticated at the proxy. Instead of showing the user
  another login page when accessing Backstage, it will handle the login in the
  -background. Backstage provides for this case a special `SignInPage` component
  +background. Backstage provides for this case the `ProxiedSignInPage` component
  which has no UI.
  Update your `createApp` call in `packages/app/src/App.tsx`, as follows.
  @@ -98,7 +98,7 @@ Update your `createApp` call in `packages/app/src/App.tsx`, as follows.
  +import { ProxiedSignInPage } from '@backstage/core-components';
  const app = createApp({
  components: {
  -+ SignInPage: props => <ProxiedSignInPage {...props} provider="oauth2-proxy" />,
  ++ SignInPage: props => <ProxiedSignInPage {...props} provider="oauth2proxy" />,
  ```
  After this, your app should be ready to leverage the OAuth2-Proxy for
  