Remove headers Cloudfront automatically includes in the response

Hi,

I've got a cloudfront distribution in front of an api that internally sends a request to an endpoint. This request includes the following headers :

user-agent content-length accept accept-encoding cloudfront-forwarded-proto cloudfront-is-desktop-viewer cloudfront-is-mobile-viewer cloudfront-is-smarttv-viewer cloudfront-is-tablet-viewer cloudfront-viewer-asn cloudfront-viewer-country content-type via x-amz-cf-id x-amzn-trace-id x-apigateway-context x-apigateway-event x-forwarded-for x-forwarded-host x-forwarded-port x-forwarded-proto

I need to remove some of them, but I can't find how. I've created a cloudfront policy to remove the x-apigateway-event but I still receive it on the target endpoint. The Api Gateway is configured as a Proxy integration, and the following message appears under "Integrations response":

Proxy integrations cannot be configured to transform responses.

Does it mean I cannot remove some headers the api gateway is including?

Thanks in advance!!