Enable Kyverno PolicyExceptions in test-values.yaml

It looks there is a typo in the test-values.yaml, resulting in PolicyExceptions from being enabled.

The current config looks like:

kyverno:
  values:
    upstream:
      features:
        policyexceptions:
          enabled: true
          namespace: 'kyverno'

but should be updated to policyExceptions: to match the values - https://repo1.dso.mil/big-bang/product/packages/kyverno/-/blob/main/chart/values.yaml?ref_type=heads#L283-286

Applying a policy exception at the moment gives an indication is not correctly enabled