Remove fields from documents based on their value

Elastic Stack Logstash
7

I have request, that works in Kibana console:

POST test_idx1/_update/1
{
"script" : "ctx._source.remove('field1')"
}

I copied it as cURL:

curl -XPOST "http://localhost:9200/test_idx1/_update/1" -H 'Content-Type: application/json' -d'{ "script" : "ctx._source.remove("field1")"}'

From which I tried to do deduct HTTP filter:

filter {
http {
url => "http://localhost:9200/test_idx1/_update/1"
verb => "POST"
user => "logstash_user"
password => "logstash_user_password"
body_format => "json"
body => "{\"script\" : \"ctx._source.remove(\\\"field1\\\")\"}"
}
}

After running Logstash no error is logged, even on DEBUG level. No update is happening in Elasticsearch.
What am I missing?