[FEATURE] removing a key-value pair from secrets

[rabessers]

We deployed Akv2k8s with Multi Key Vault Secret.

When we remove a key-value pair from Azure Key Vault, that key-value pair is not deleted from the Kubernetes secret object while syncing.

For example, you can put those values to Azure Vault:

{ "key1": "value1", "key2": "value2", "key3": "value3" }

If we delete "key3": "value3" pair from Azure Vault Console, the deletion is not syncing with the secret object. I disabled the previous Azure Key Vault version but still that key-value stays inside secrets.
There is no problem with adding a new key-value pair or updating an existing one.

This issue is similar with #732