docs: update Chart.yaml to reflect requiredSecretKeys rename

Update changelog annotation to use the correct field name
'requiredSecretKeys' instead of 'secretKeys' to match the
implemented changes.

Signed-off-by: Pierluigi Lenoci <pierluigi.lenoci@gmail.com>

Author: pierluigilenoci

helm/oauth2-proxy/Chart.yaml

@@ -31,7 +31,7 @@ kubeVersion: ">=1.16.0-0"
 annotations:
   artifacthub.io/changes: |
     - kind: added
-      description: Added config.secretKeys option to selectively include secrets (allows excluding client-secret for federated auth scenarios)
+      description: Added config.requiredSecretKeys option to selectively include secrets (allows excluding client-secret for federated auth scenarios)
       links:
         - name: Github PR
           url: https://github.com/oauth2-proxy/manifests/pull/384