fix(release notes): remove Mixer adapter deprecation notice (#5018)
fix(release notes): remove Mixer adapter deprecation notice (#5018)

Signed-off-by: Douglas Reid <5824f1293f78a6d336a38973f53e0782b086eb89@google.com>
istio/istio.io,istio/istio.io,istio/istio.io,istio/istio.io,istio/istio.io,istio/istio.io,istio/istio.io