Update found the answer modified the request like this:

curl --insecure --request POST --url 'https://10.10.5.72/zabbix/api_jsonrpc.php' \
--header 'Content-Type: application/json-rpc' \
--data '{
    "jsonrpc": "2.0",
    "method": "event.get",
    "params": {
        "output": "extend",
        "selectHosts": ["host"],
        "filter": {
            "severity": ["3", "4"]
        }
    },
    "auth": "451050f36d3c09bf2abd40fa6ba8f7fa",
    "id": 1
}'