message: update github readme to include owners filter
diff: @@ -92,11 +92,11 @@ integrations:
  ### Limiting the GitHub App installations
  If you want to limit the GitHub app installations visible to backstage you may
  -optionally include the `allowedInstallationIds` option.
  +optionally include the `allowedInstallationOwners` option.
  ```yaml
  appId: 1
  -allowedInstallationIds: [1234]
  +allowedInstallationOwners: [1234]
  clientId: client id
  clientSecret: client secret
  webhookSecret: webhook secret
  