docs/policy-reference: add 'in' operator examples (#3914)
docs/policy-reference: add 'in' operator examples (#3914)

Signed-off-by: Stephan Renatus <0d0a21c7604d0d452d5c1019ca18e48a97a9a057@gmail.com>
open-policy-agent/opa,tsandall/opa,tsandall/opa,open-policy-agent/opa,open-policy-agent/opa,tsandall/opa,open-policy-agent/opa,tsandall/opa,tsandall/opa,open-policy-agent/opa,tsandall/opa,open-policy-agent/opa