message: docs/oauth2-proxy: update provider installation example
diff: @@ -40,7 +40,9 @@ or grab ID or access tokens to look up additional information and/or validate th
  A simple sign-in resolver might for example look like this:
  ```ts
  -providers.oauth2Proxy.create({
  +providerFactories: {
  + ...defaultAuthProviderFactories,
  + oauth2Proxy: providers.oauth2Proxy.create({
  signIn: {
  async resolver({ result }, ctx) {
  const name = result.getHeader('x-forwarded-user');
  @@ -53,6 +55,7 @@ providers.oauth2Proxy.create({
  },
  },
  }),
  +},
  ```
  ## Adding the provider to the Backstage frontend
  