docs/olm-integration: Add image registry config reference link (#5016)

The reference link is based on the link in golang/quickstart page:
https://github.com/operator-framework/operator-sdk/blob/f298f7c92ee154a0e8123fb13398a7f21720cf0e/website/content/en/docs/building-operators/golang/quickstart.md#L59 .

Signed-off-by: Sunny <[email protected]>

Author: darkowlzz

website/content/en/docs/olm-integration/testing-deployment.md

@@ -176,3 +176,4 @@ Let's look at the anatomy of the `cleanup` configuration model:
 [cli-olm-status]:/docs/cli/operator-sdk_olm_status
 [creating-bundles]:/docs/olm-integration/quickstart-bundle/#creating-a-bundle
 [add-sa-secret]:https://kubernetes.io/docs/tasks/configure-pod-container/configure-service-account/#add-imagepullsecrets-to-a-service-account
+[image-reg-config]:/docs/olm-integration/cli-overview#private-bundle-and-catalog-image-registries