Remove kustomize link in secrets.md doc (flyteorg#5043)

Signed-off-by: Ryan Lo <[email protected]>

docs/user_guide/productionizing/secrets.md

@@ -372,8 +372,6 @@ The following secret managers are available at the time of writing:
 - [AWS Secret Manager](https://docs.aws.amazon.com/secretsmanager/latest/userguide/create_secret.html): `flyte-pod-webhook` will add the AWS Secret Manager sidecar container to a task Pod which will mount the secret.
 - [Vault Agent Injector](https://developer.hashicorp.com/vault/tutorials/getting-started/getting-started-first-secret#write-a-secret) : `flyte-pod-webhook` will annotate the task Pod with the respective Vault annotations that trigger an existing Vault Agent Injector to retrieve the specified secret Key from a vault path defined as secret Group.
 
-You can configure the additional secret manager by defining `secretManagerType` to be either 'K8s', 'AWS' or 'Vault' in
-the [core config](https://github.com/flyteorg/flyte/blob/master/kustomize/base/single_cluster/headless/config/propeller/core.yaml#L34) of the Flytepropeller.
 
 When using the K8s secret manager plugin, which is enabled by default, the secrets need to be available in the same namespace as the task execution
 (for example `flytesnacks-development`). K8s secrets can be mounted as either files or injected as environment variables into the task pod,